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I'm trying to find out what kind of spider is this little fellow:
It really seems to like our garage and is the bane of my girlfriend (as evidenced by all the screaming when on two occasions one got into our home somehow). I was never able to spot this kind outdoors, which is rather odd (there are plenty of Araneus diadematus spiders in the area which are fairly easy to spot).
It's hard to tell on the photo, but these spiders seem rather big (at least as far as spiders in Poland I was able to spot go)… somewhere around 5cm at least (legs included)? They really do make for rather large, black spots against an otherwise white garage wall.
I'd really like to find what kind of species this is so that I can, hopefully, convince my GF that it's harmless to humans. Unless it isn't, in which case I'll start getting scared of walking into our garage. ;)
PS. We live in Poland, Poznań.
I think this is just Tegenaria domestica. I am from Czech republic and this is really big and kinde everywhere. Specialy in garages.
I'm not a European spider pro, so although I think it looks rather like a Tegenaria, I can't be positive it isn't something else that I'm unfamiliar with.
However, I can state confidently that it is not any of the problem biters known on Earth. In Europe, you're going to be careful around any of the Black Widow group (Latrodectus spp.) and perhaps be cautious if you should come across a Mediterranean Recluse (Loxosceles rufescens) - but this isn't either of those possibilities. Widows are small, globular cobweb spiders with relatively short, arched legs, and Recluses are very plain spiders with a dark central 'fiddle' mark on the 'head'. By elimination, if it isn't any of the known problem biters, it's harmless.
However, what you can do to get a better identification, is to submit your photo to Ed Nieuwenhuys at his website which deals with European spiders.
K.S. HAGEN , . J.A. MCMURTRY , in Handbook of Biological Control , 1999
Araneidae and Tetragnathidae
Orb weavers in the families Araneidae and Tetragnathidae are also frequently mentioned as comprising a large proportion of the spider faunas in some ecosystems. Their abundance and estimated predation pressure on insect populations in grassland ecosystems was pointed out by Nyffeler and Benz (1987) . Orb weavers are the dominant group in some crops, such as cotton and soybeans, in the United States ( Whitcomb & Bell, 1964 LeSar & Unzicker, 1978 Nyffeler et al., 1989 Young & Edwards, 1990 ). In general, these spiders are limited to drifting, flying, or hopping prey ensnared in the webs. There is no conclusive evidence that they are significant biological control agents on crops, but experimental studies are lacking.
The term ecdysis comes from Ancient Greek: ἐκδύω (ekduo), "to take off, strip off". 
In preparation for ecdysis, the arthropod becomes inactive for a period of time, undergoing apolysis or separation of the old exoskeleton from the underlying epidermal cells. For most organisms, the resting period is a stage of preparation during which the secretion of fluid from the moulting glands of the epidermal layer and the loosening of the underpart of the cuticle occur. Once the old cuticle has separated from the epidermis, a digesting fluid is secreted into the space between them. However, this fluid remains inactive until the upper part of the new cuticle has been formed. Then, by crawling movements, the organism pushes forward in the old integumentary shell, which splits down the back allowing the animal to emerge. Often, this initial crack is caused by a combination of movement and increase in blood pressure within the body, forcing an expansion across its exoskeleton, leading to an eventual crack that allows for certain organisms such as spiders to extricate themselves. While the old cuticle is being digested, the new layer is secreted. All cuticular structures are shed at ecdysis, including the inner parts of the exoskeleton, which includes terminal linings of the alimentary tract and of the tracheae if they are present.
Each stage of development between moults for insects in the taxon endopterygota is called an instar, or stadium, and each stage between moults of insects in the Exopterygota is called a nymph: there may be up to 15 nymphal stages. Endopterygota tend to have only four or five instars. Endopterygotes have more alternatives to moulting, such as expansion of the cuticle and collapse of air sacs to allow growth of internal organs.
The process of moulting in insects begins with the separation of the cuticle from the underlying epidermal cells (apolysis) and ends with the shedding of the old cuticle (ecdysis). In many species it is initiated by an increase in the hormone ecdysone. This hormone causes:
- apolysis – the separation of the cuticle from the epidermis of new cuticle materials beneath the old
- degradation of the old cuticle
After apolysis the insect is known as a pharate. Moulting fluid is then secreted into the exuvial space between the old cuticle and the epidermis, this contains inactive enzymes which are activated only after the new epicuticle is secreted. This prevents the new procuticle from getting digested as it is laid down. The lower regions of the old cuticle, the endocuticle and mesocuticle, are then digested by the enzymes and subsequently absorbed. The exocuticle and epicuticle resist digestion and are hence shed at ecdysis.
Spiders generally change their skin for the first time while still inside the egg sac, and the spiderling that emerges broadly resembles the adult. The number of moults varies, both between species and sexes, but generally will be between five times and nine times before the spider reaches maturity. Not surprisingly, since males are generally smaller than females, the males of many species mature faster and do not undergo ecdysis as many times as the females before maturing. Members of the Mygalomorphae are very long-lived, sometimes 20 years or more they moult annually even after they mature.
Spiders stop feeding at some time before moulting, usually for several days. The physiological processes of releasing the old exoskeleton from the tissues beneath typically cause various colour changes, such as darkening. If the old exoskeleton is not too thick it may be possible to see new structures, such as setae, from outside. However, contact between the nerves and the old exoskeleton is maintained until a very late stage in the process.
The new, teneral exoskeleton has to accommodate a larger frame than the previous instar, while the spider has had to fit into the previous exoskeleton until it has been shed. This means the spider does not fill out the new exoskeleton completely, so it commonly appears somewhat wrinkled.
Most species of spiders hang from silk during the entire process, either dangling from a drop line, or fastening their claws into webbed fibres attached to a suitable base. The discarded, dried exoskeleton typically remains hanging where it was abandoned once the spider has left.
To open the old exoskeleton, the spider generally contracts its abdomen (opisthosoma) to supply enough fluid to pump into the prosoma with sufficient pressure to crack it open along its lines of weakness. The carapace lifts off from the front, like a helmet, as its surrounding skin ruptures, but it remains attached at the back. Now the spider works its limbs free and typically winds up dangling by a new thread of silk attached to its own exuviae, which in turn hang from the original silk attachment.
At this point the spider is a callow it is teneral and vulnerable. As it dangles, its exoskeleton hardens and takes shape. The process may take minutes in small spiders, or some hours in the larger Mygalomorphs. Some spiders, such as some Synema species, members of the Thomisidae (crab spiders), mate while the female is still callow, during which time she is unable to eat the male. 
Eurypterids are a group of chelicerates that became extinct in the Late Permian. They underwent ecdysis similarly to extant chelicerates, and most fossils are thought to be of exuviae, rather than cadavers. 
Spiders – The Generalist Super Predators in Agro-Ecosystems
15.6 Estimates of Spider Species Diversity
Roughly 34,000 species of spiders had been named by 1988, placed in about 3000 genera and 105 families ( Platnick, 1989 ). A small percentage of those species names will turn out to be synonyms. Families with over 1000 species described are Salticidae (jumping spiders ca. 490 genera, 4400 species), Linyphiidae (dwarf or money spiders, sheet web weavers ca. 400 genera, 3700 species), Araneidae (common or web weavers ca. 160 genera, 2600 species), Theridiidae (cob web weavers ca. 50 genera, 2200 species), Lycosidae (wolf spiders ca. 100 genera, 2200 species), Gnaphosidae (ground spiders ca. 140 genera, 2200 species), and Thomisidae (crab spiders ca. 160 genera, 2000 species). Although the aforementioned families are cosmopolitan, the Linyphiids are most diverse in the north temperate regions, whereas the others are most diverse in the tropics or show no particular pattern. Because spiders are not thoroughly studied, estimates of total species diversity are difficult. The fauna of Western Europe (especially England) and Japan are most completely known ( Roberts, 1985, 1987 Yaginuma, 1977 ). The Nearctic fauna is perhaps 80% described ( Coddington et al., 1990 ), New Zealand perhaps 60–70% ( Court and Forster, 1988 Forster, 1967 Forster and Blest, 1979 Forster and Wilton, 1973 ) and Australia perhaps 20% ( Raven, 1988 ). Other areas, especially Latin America, Africa and the Pacific region are much more poorly known. About one-third of all genera (1090 in 83 families) occur in the Neotropics. If the above statistics suggest that 20% of the world fauna have been described, then about 170,000 species of spiders are extant and yet to be discovered. In India, only during the post-independence period was work on spider systematics, ecology and biology started ( Tikader, 1962 Samiayyan, 1996 ).
What is IPM?
The two-spotted spider mite (TSSM), Tetranychus urticae, is a common pest in greenhouses with a wide host range including specialty annuals and bedding plants, herbaceous perennials, vegetables and herbs.
Biology and Life Cycle
Adult female two-spotted spider mites can live for about one month. During this time, they may lay from 100 to 200 eggs. Mite eggs are small, spherical in shape and are laid on the underside of leaves. Eggs hatch in about three days and the young mite larvae begin feeding. After transitioning through two nymphal stages, mites become adults. Optimum temperatures for spider mite development are between 85 to 95 o F with a lower threshold for development of 54°F and an upper threshold of 104° F. The life cycle from egg to adult can be completed in as little as 7 days at temperatures greater than 85˚ F and low relative humidity levels of 20 to 40%.
Female mites are three times more abundant than males. Fertilized adult females produce both males and females. Unfertilized adult females only produce males. Males have only one set of genes, so mutations such as pesticide resistance, are immediately expressed. Incorporating biological control strategies into your pest management program can help slow down the development of resistance.
During adverse conditions of decreasing day length, falling temperatures and decline in food supply, adult females enter a resting or overwintering stage known as diapause. Females turn bright orange red and hide in concealed places within the greenhouse. Do not confuse this resting stage with the beneficial predatory mite, Phytoseiulus persimilis, which is a bright orange color without the two dark spots.
Figure 1: Bright orange diapausing spider mite compared to TSSM. Photo by L. Pundt
Biological controls are best used preventatively, when spider mite populations are low. Weekly scouting and random plant inspections are needed to detect populations early. Carefully inspect plants in hot, dry areas of a greenhouse or where there is no overhead irrigation that wets the foliage that may wash some of the mites off the plant leaves. Regularly inspect the most susceptible cultivars or species, and look for signs of plant damage. As spider mites insert their stylet-like mouthparts into plant tissue, they suck out plant juices removing the chlorophyll. At first, you see a slight flecking or stippling (chlorotic spot) on the leaves.
Figure 2: Flecking or stippling on Buddleia leaf. Photo by L. Pundt
Figure 3: Spider mite damage on ivy geraniums resembles edema. Photo by L. Pundt
Thin-leaved plants such as garden impatiens may show injury more quickly than thick-leaved plants such as ivy geraniums. Mite feeding damage on ivy geraniums is also often mistaken for edema. As spider mite feeding continues, leaves turn yellow, bronzed and drop from the plant. When high mite populations develop, the fine webbing is extensive. Tag pest-infested plants as indicator plants to determine the effectiveness of biological control measures. A 10x to 20x hand lens is helpful to detect all stages of the mites. Because mites are easily carried on workers or their clothing, one should do routine greenhouse tasks and scout in mite-infested areas at the end of the day.
Predatory mites, predatory midges and predatory beetles can all be used in a biological control program. Different species of predatory mites (Phytoseiulus persimilis), Neoseiulus (Amblyseius californicus, Amblyseius andersonii, Galendromus occidentalis, Mesoseiulus longipes, Neoseiulus (Amblyseius) fallacis are each adapted to different environmental conditions (temperature and relative humidity levels). A predatory midge (Feltiella acarisuga) and a predatory ladybeetle (Stethorus punctillum) are also commercially available.
Some of the biological control agents used against thrips such as Neoseiulus (Amblyseius) cucumeris, Orius sp. and Amblyseius swirskii may also feed on spider mites but cannot be relied upon for control. The generalist aphid predator, Chrysoperla spp. may also feed upon spider mites. Some growers may also release the generalist predatory soil dwelling mite, Hypoaspis miles (Stratiolaelaps scimitus) near perimeter walls, for use against the diapausing spider mites that are hiding in concealed places.
Phytoseiulus persimilis, a predatory mite
Adult Phytoseiulus persimilis feeds on all stages of two-spotted spider mites. This specialist predator can only survive by feeding upon two-spotted spider mites. The adult P. persimilis is bright red in color, pear shaped, long-legged and slightly larger and more active than spider mites.
Figure 4: Phytoseiulus persimilis, an important predator of two spotted spider mites. Photo by L. Pundt
Adult females lay eggs that are about 3x the size of two-spotted spider mite eggs and are also more football shaped than the round two spotted spider mite eggs.
The development time for P. persimilis is shorter than for spider mites about 5 days at 86°F, 9 days at 68°F, and 25 days at 59°F. At temperatures above 86°F, P. persimilis can&rsquot keep up with the reproduction of two spotted spider mites. At low relative humidity (less than 60%), eggs shrivel and do not hatch. Optimum conditions are relative humidities above 75% and temperatures over 68˚ F.
P. persimilis is attracted to the chemical odors produced by plants infected with spider mites as it searches for its prey by touch and scent. Both adults and nymphs actively search plants for two-spotted spider mites. P. persimilis can spread through a greenhouse as long as plant leaves are in contact with each other. This biological control agent has been used in commercial greenhouses, (especially greenhouse vegetables) since the 1960&rsquos. However, the glandular hairs on greenhouse tomato leaves reduce its dispersal.
Tips for P. persimilis use
- Release early when mite populations are low and two spotted spider mites are first noticed.
- This voracious, specialist predatory mite needs to have spider mite prey or it will disperse or starve.
- P. persimilis is available either in a granular carrier or on bean leaves with all life stages and a food source.
- When using carrier product, check first by sprinkling some of the product unto a white sheet of paper and look for the active predatory mites.
- Gently roll the tube to mix the predatory mites in the carrier before application.
- Sprinkle material on leaves.
- Concentrate releases near hot spots of mite activity.
- Relative humidity should be greater than 75% and temperature above 68°F for some hours of the day. Lightly misting plants or walkways may increase humidity levels.
- Adults and nymphs actively search for prey and suck them dry.
- Spider mite colonies should be reduced in 2 to 3 weeks.
- Contact your supplier for information on release rates. Supplier recommended release rates vary depending upon susceptibility of crops or cultivars to spider mites, length of crop time and infestation levels.
- To evaluate effectiveness, look for dead, shriveled spider mites that have been fed upon.
- For information on pesticide compatibility: consult with your supplier or with the following resources on the Internet:
- Pesticide Side Effects Database- www.koppert.com
- Pesticide Side Effects Database &ndash www.biobest.be
Neoseilus (Amblyseius) californicus, a predatory mite
Neoseilus (Amblyseius) californicus is slower acting than P. persimilis but has a broader host range than P. persimilis and survives longer in the absence of prey by feeding upon other plant feeding mites (such as broad and cyclamen mites) and thrips. N. californicus may also feed upon mold and nectar. This slow acting predatory mite is useful for keeping low spider mite populations under control and can be released preventively. In situations where high temperature or relative humidity variations can occur, N. californicus may be a better choice than P. persmilis. You can also release N. californicus in combination with P. persmilis.
Tips for N. californicus use
- Release as soon as possible after receiving.
- It is available in a granular carrier or in breeding sachets.
- Gently roll the tub to mix the predatory mites in the carrier before application.
- N. californicus is active at temperatures between 46°F to 95°F, 40-80% RH.
- Consult with your supplier for information on release rates.
- For detailed information on pesticide compatibility: consult with your supplier or with the following resources on the Internet:
- Pesticide Side Effects Database- www.koppert.com
- Pesticide Side Effects Database &ndash www.biobest.be
Amblyseius andersonii,a predatory mite
This predatory mite feeds upon spider mites, broad mites, cyclamen mites and eriophyid mites. It may also survive on thrips and fungal spores in the absence of mites. A. andersonii can be released when there are low numbers of spider mites. If hot spots develop, P. persimilis can be used with A. andersonii. A. andersonii is active at a wide range of temperatures (42 - 104 ˚F) and can be applied to both greenhouse and outdoor crops. It is available in a granular carrier or in breeding sachets.
Neoseilus (Amblyseius) fallacis,a predatory mite
This predatory mite feeds upon spider mites, tomato rust mites and cyclamen mites. The shiny pear shaped adults (1/50 inch long) are tan to light orange in color with long legs. N. fallacis can survive in the absence of prey on other small arthropods and pollen. N. fallacis tolerates a wide range of temperatures (48-85˚ F) but does best where there is a dense plant canopy and relative humidity over 50%. N. fallacis is available on bean leaves or in a granular carrier. You can also release N. fallacies in combination with P. persmilis.
Galendromus occidentalis,a predatory mite
This predatory mite feeds upon two- spotted spider mites. G. occidentalis does best are temperatures between 50-115˚ F and 30 to 60% relative humidity. If mite populations are low, G. occidentalis can feed upon pollen. G. occidentalis is available in a granular carrier.
Mesoseilus longipes,a predatory mite
This predatory mite feeds upon spider mites and does best at temperatures between 80-90 ˚F but can tolerate lower humidity levels (40% RH at 70˚ F).
Feltiella acarisuga, a predatory midge
A small (1/16 of an inch long) predatory gall midge (Feltiella acarisuga) feeds on two-spotted spider mites. (Another species of gall midge is commercially available for use against aphids.) Adults live for 2 or 3 days, are more active at night and rest during the day on the underside of leaves. Females lay orange to red eggs among the spider mite colonies, eggs hatch in 3 to 5 days. The larvae stage is the only predacious stage.
Figure 5: Predatory midge larvae. Photo by L. Pundt
After about a week of feeding, larvae pupate on the underside of leaves forming tiny, white velutinous pupal cocoons.
Figure 6. Feltiella acarisuga pupae, Photo by L. Pundt
Adults emerge from the pupae. Feltella develops from egg to adult in 10 days at 80° F to 34 days at 59°F with relative humidity between 60 to 95%. Extended periods of relative humidity below 60% may reduce their survival and reproduction, optimum relative humidity is 80%. This predatory mite is active year round and does not have a winter resting stage.
Feltiella is shipped in the pupal stage and adults emerge soon after arrival. They are best released late at night or early in the morning. Felitella can be used with P. persmilis (depending upon the crop and pest levels). Adults are excellent flyers so they may be able to reach handing baskets and other hard to reach ornamental crops. Feltiella is also able to forage on the hairy leaves of greenhouse tomatoes whereas the tomato&rsquos glandular hairs reduce the survival and reproduction of P. persmilis.
Tips for Feltiella acarisuga use
- Commercially available as pupae on paper pieces in pots or boxes. Pierce paper disc on the cover, so the adult midges can emerge.
- Open the box containing the predatory midges, place close to spider mite infestations. Let box stand for one week until adults have emerged.
- When scouting, look for the nearly white pupal cases near the midrib on the leaf undersides and for the bright orange larvae.
- For more detailed information on pesticide compatibility: consult with your supplier or with the following resources on the Internet:
- Pesticide Side Effects Database- www.koppert.com
- Pesticide Side Effects Database &ndash www.biobest.be
Stethorus punctillum,a predatory ladybird beetle
This small, (1/10 of an inch long) black predatory beetle feeds on all life stages of spider mites. Adults can fly, allowing them to locate spider mite colonies that are not accessible to predatory mites. Their yellow oval eggs are laid singly in or near mite colonies. Larvae are slow moving with conspicuous legs. Larvae and adults feed on all stages of spider mites. Optimum conditions are moderate to high temperatures (61-90˚ F). They can also feed on small arthropod eggs, aphids, nectar, and pollen. Stethorus prefer smooth leaved plants and can&rsquot readily travel the hairy leaves of greenhouse tomatoes. These predatory ladybird beetles are best used in combination with predatory mites.
Regular monitoring, in conjunction with cultural controls help insure the successful use of predatory mites, midges and beetles against spider mites.
Cloyd, R. 2008. All predatory mites are not created equal. Greenhouse Grower. June 2008.
Gillespie, D. R., G. Opit and B. Roitberg. 2000. Effects of Temperature and Relative humidity on Development, Reproduction, and Predation in Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae). Biological Control. 17. 132-138.
Glenister, C. 2005. Midge Out-Muscles Spider Mites. GMPro. Feb 2005. 35-38.
Heinz, K.M., R.G. Van Driesche, and M.P. Parella (ed.) 2004. Bio Control in Protected Culture. Ball Publishing, Batavia, Il. 522 pp.
Lamb, E. and B. Eshenaur. 2014. Greenhouse Biocontrol Workbook. NYS Integrated Pest Management Program. Cornell University Cooperative Extension. 84 pp. http://www.nysipm.cornell.edu/
Stack, Lois Berg. (ed). 2014-2015. New England Greenhouse Floriculture Guide. A Management Guide for Insects, Diseases, Weeds and Growth Regulators. New England Floriculture Inc and the New England State Universities.
Malais, M.H. and W. J. Ravensberg. 2003. Knowing and Recognizing: The biology of glasshouse pests and their natural enemies. Koppert Biological Systems and Reed Business Information. The Netherlands. 288 pp.
Opit, G. P., G.K. Fitch, D.C. Margolies, J. R. Nechols, and K. A. Williams. 2006. Overhead and Drip-tube Irrigation Affect Twospotted Spider Mites and their Biological Control by a Predatory Mite on Impatiens. HortScience. 41(3):691-694
Osborne, L. S., L. E. Ehler, and J. R. Nechols. 1999. Biological Control of the Twospotted Spider Mite in Greenhouses. University of Florida. Bulletin 853. http://www.mrec.ifas.ufl.edu/lso/SpMite/b853a1.htm
Smith, T. and L. Pundt. 2014. Greenhouse Pest Guide web App. http://tiny.cc/greenhousepestguide.
Thomas, C. 2005. Greenhouse IPM with an Emphasis on Biocontrol. Publication No. AGRS-96. 89 pp. Pennsylvania Integrated Pest Management Program.
By Leanne Pundt, Extension Educator, University of Connecticut, 2007, updated 2014
Disclaimer for Fact Sheets:
The information in this document is for educational purposes only. The recommendations contained are based on the best available knowledge at the time of publication. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. UConn Extension does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available. The University of Connecticut, UConn Extension, College of Agriculture, Health and Natural Resources is an equal opportunit
Biological Eradication of Spider Mites Using Mother Nature
-A Practical Guide To Farming Quality Cannabis 6 Hemp
Written by: Daniel Enking, Everflux Technologies Founder & CEO Bran Wachsman
Known as Tetranychidae in the scientific world, and simply Spider Mites to cannabis and hemp farmers, these common crop-destroying pests seem to come with the job description. There are many subspecies of spider mites, and our focus today is on the Two-Spotted Spider Mite. Some of the unique species are much more easily identified than others however, it is generally unwise to try, as their control measures, damage and biology are all the same!
Learn more as Everflux Technologies online articles teach you about how to combat pest issues by using mother nature instead of toxic and costly pesticides. Identification & Life Cycle Spider mite populations WILL proliferate under the right conditions. Unfortunately, these conditions exist in many indoor grows - basically, warm with very little wind. Infestation damage can be identified by the telltale sign of the webbing they produce on your cannabis/hemp fan leaves. Inspecting for spider mites has become a daily chore for many grower teams. What your team needs to understand is that by the time you see webbing, it may be too late!
The Four Life Stages Of Spider Mites:
Eggs – Over the hotter and ideal growing season, they can be found on the undersides of fan leaves along with stalks and stems.
Larva – Newly laid eggs start hatching after the last frost has passed. The larva has six legs, and almost no feeding is done during this life stage cycle.
Nymph – Are similar to the adult but slightly smaller and unable to reproduce at this point in the life cycle. There are two nymph stages: proto-nymph and deutonymph.
Adult – Adult spider mites vary from pale brown, orange, green, or yellow and are about 0.4 mm long with eight legs.
The species females lay between 50-100 eggs throughout their lives with unfertilized eggs hatching as males and fertilized eggs hatching as females.
There are two approaches to using augmentation biological control. First, it can be used as a preventive measure to provide long-term control and keep pest populations from reaching excessive numbers. This type of augmentation is called inoculation. With inoculation, small numbers of a natural enemy are released early in the pest cycle to prevent the pest population from building. Ideally, the natural enemies reproduce and build in numbers along with the pest population to provide continued control throughout the season.
Augmentation also can be used to treat a pest outbreak by overwhelming a pest with the sudden introduction of large numbers of predators. This approach is called inundation, and involves the mass release of large numbers of natural enemies to provide a quick, knockdown effect on the pest population. In this way, augmentation can be used as a remedial treatment to manage a pest problem in the same way chemicals are often used. The use of microbial pesticides such as Bt, Bacillus thuringiensis, is also a form of inundation biological control.
In both inundative and inoculative augmentation, the goal is not to permanently establish the natural enemy into the landscape, but rather provide mortality for a short time period, perhaps one growing season or a critical point during the season. Augmentation biological control does not replace natural mortality, but simply provides an additional source of control. It is compatible with conservation biological control as well as cultural, physical and mechanical pest management strategies.
Sticky Science: the Evolution of Spider Webs
It may seem silly to fear a little spider&mdashbut the predator&rsquos appearances in horror movies make more sense when you consider the precision, skill and creativity it employs to target its prey. Spiders&rsquo venom-injecting fangs and the pointy claws tipping their segmented legs are menacing enough, but their innovative use of silk to ensnare victims may be the biggest reason to be grateful they are small.
&ldquoThey&rsquore absolute masters of using silk,&rdquo says Paul Selden, an arachnologist and paleontologist at the University of Kansas. Other creepie-crawlies make the stuff, too&mdashsilkworms use it pupate in, some ants make nests from it&mdashbut, says Selden, &ldquothey don&rsquot have the great variety of uses that spiders do.&rdquo
Spider silk is put to work in dozens of ways&mdashto protect eggs, to create underwater homes and, most conspicuously, as hunting tools of stunning diversity. In the tree depicted below, scientists have sketched out a sampling of web designs of orb weavers and spiders that descended from them&mdashjust a subset of the spiders that use silk to hunt. The ground and trunk are occupied by ancestral relatives and some of the silk structures that preceded those suspended in the branches.
Orb weavers, sometimes classified along with their descendants into a grouping called Orbiculariae, comprise about a quarter of the more than 45,000 known spider species. Their webs typically feature the classic concentric circle and spoke-like strands that radiate from a hub. But some Orbiculariae members spin novelties. In the figure, a bolas spider (Mastophora) hangs from the tree&rsquos highest point, prepared to swing her sticky sphere at moths drawn in by a pheromone lure. To the right, a net-casting spider (Deinopis) holds a silken trawl between her claws, ready to drop it when her quarry wanders underneath.Orb weavers, from the grouping Orbiculariae, make the classic, wheel-shaped spider web, as well as other intriguing designs. This tree hosts a sampling of Orbiculariae illustrating the web diversity. Evolutionarily older spiders and their ancestors appear on the ground and trunk more recent arrivals hang from the highest branches. Credit: F. Vollrath and P. Selden AR Ecology, Evolution, and Systematics 2007 (modified from Vollrath 1988)
Scientists are still working to classify this diversity and understand how it got here, says Selden, who coauthored a review on spider web evolution in the Annual Review of Ecology, Evolution, and Systematics. This picture from the review hints at a general evolutionary progression as one moves up the tree, and highlights a pivotal event: As insects took to flight, spiders chased up after them, placing their snares higher in the air.
The webs continued to diversify as insects evolved ways to escape this clade of predators. Scoloderus&rsquo ladder web, which sports an elongated, crosshatched netting above a typical, circular orb, is specialized to target moths, which would normally escape a sticky web by shedding protective scales. The ladder portion keeps the moth tumbling&mdashand will trap it when the scales have all flaked off. The triangle spider (Hyptiotes) optimizes its attack by releasing the long-thread portion of its web when an insect hits the main, cone-shaped portion. As a result, the web collapses and envelops the target, like a camping tent that has suddenly lost its poles.
A bit of stickiness helps keep prey in place long enough for a spider to permanently subdue them. But not all webs get their stick the same way. Some webs snag insects with droplets of glue. Others are &ldquowooly&rdquo&mdashtheir silk is made of thin strands that cling to an insect&rsquos hairs and legs, much like the threads of a sweater stick to a bur. In the illustration, spiders on the right main trunk of the tree weave wooly&mdashor cribellate&mdashwebs. And weavers on the left use gluey, ecribellate silk.
This divergence in strand type has been a sticking point for scientists studying spider evolution, spinning out a long debate over how many times the orb web evolved. Though web strands may be very different, the building behaviors are remarkably similar, says Jason Bond, an arachnologist at the University of California, Davis. So it&rsquos unclear whether orb weaving arose independently in cribellate and ecribellate weavers, or whether the web arose once and silk type diverged later on.
Clues about the evolution of web-building behavior have come in part from fossil evidence. Webs and other silken structures typically don&rsquot fossilize well (though occasionally, scientists have found strands of silk and clumps of web preserved in amber), so researchers often rely on the connections they can make between present-day spider morphology and behavior to tell them something about spiders and proto-spiders of the past.
For example, today&rsquos sheet web builders (such as the Agelena group pictured, and funnel-web spiders of the Ischnothele genus) lay blankets of webbing across grass and other vegetation and tend to exhibit unusually long spinnerets. Just this year, scientists noted similarly long spinnerets in the recently discovered fossilized remains of ancient arachnids. Thus, &ldquoat least one hypothesis would be that they built a type of sheet web,&rdquo says Bond. &ldquoMaybe sheet webs are the type of web that&rsquos ancestral for all spiders.&rdquo
As well as studying how spider webs came about, researchers also are looking at how some spiders came to abandon them. Some newer species, such as certain ant-hunting specialists and the portia jumping spider (which will prey on fellow spiders by lowering itself from above), don&rsquot use webs at all.
The mind-boggling diversity of spider strategies shouldn&rsquot come as such a surprise when one considers that they have had hundreds of millions of years to evolve&mdashresearchers have found fossils of spiders that were scuttling around more than 150 million years before the dinosaurs.
&ldquoYou&rsquore talking about 50,000 species of things that are all nearly exclusively predatory,&rdquo says Bond. &ldquoSpiders have devised all sorts of ways of killing insects.&rdquo
*Editor&rsquos Note (10/31/18): The subheading of this story has been updated to correct an error in the number of years spiders have been evolving.
This article was originally published on October 31, 2018 by Knowable Magazine, an independent journalistic endeavor from Annual Reviews, and is reprinted with permission. Sign up for the newsletter.
ANN ARBOR—Warning to arachnophobes and the faint of heart: This is the stuff of nightmares, so you might want to proceed with caution.
A University of Michigan-led team of biologists has documented 15 rare and disturbing predator-prey interactions in the Amazon rainforest including keep-you-up-at-night images of a dinner plate-size tarantula dragging a young opossum across the forest floor.
The photos are part of a new journal article titled “Ecological interactions between arthropods and small vertebrates in a lowland Amazon rainforest.” Arthropods are invertebrate animals with segmented bodies and jointed appendages that include insects, arachnids (spiders, scorpions, mites and ticks) and crustaceans.
The article, published online Feb. 28 in Amphibian & Reptile Conservation, details instances of arthropod predators—mostly large spiders along with a few centipedes and a giant water bug—preying on vertebrates such as frogs and tadpoles, lizards, snakes, and even a small opossum.
A wandering spider (Ctenidae) preying on a subadult Cercosaura eigenmanni lizard. Photo by Mark Cowan, in Amphibian & Reptile Conservation (amphibian-reptile-conservation.org).
“This is an underappreciated source of mortality among vertebrates,” said University of Michigan evolutionary biologist Daniel Rabosky. “A surprising amount of death of small vertebrates in the Amazon is likely due to arthropods such as big spiders and centipedes.”
Once or twice a year, Rabosky leads a team of U-M researchers (faculty members, postdocs, graduate students and undergraduates) and international collaborators on a month-long expedition to the Los Amigos Biological Station in the remote Madre de Dios region of southeastern Peru.
“We were pretty ecstatic and shocked, and we couldn’t really believe what we were seeing, we knew we were witnessing something pretty special, but we weren’t aware that it was the first observation until after the fact.”
The study site, in lowland Amazon rainforest near the Andes foothills, is in the heart of one of the most diverse ecosystems on the planet. The team’s main research focus is the ecology of reptiles and amphibians. But over the years, the scientists have witnessed and documented numerous interactions between arthropod predators and vertebrate prey.
“We kept recording these events, and at some point we realized that we had enough observations to put them together in a paper,” said Rabosky, an associate professor in the Department of Ecology and Evolutionary Biology and an associate curator at the U-M Museum of Zoology.
Spiders are among the most diverse arthropod predators in the tropics, and previous reports of spider predation in the Amazon include prey from all major vertebrate taxonomic groups: fish, amphibians, reptiles, birds and mammals.
But knowledge of these interactions remains limited, especially given the diversity of vertebrate prey and potential arthropod predators in species-rich tropical communities. The new paper includes observations from 2008, 2012, 2016 and 2017.
“These events offer a snapshot of the many connections that shape food webs, and they provide insights into an important source of vertebrate mortality that appears to be less common outside the tropics,” said the study’s first author, Rudolf von May, a postdoctoral researcher in Rabosky’s lab.
“Where we do this research there are about 85 species of amphibians—mostly frogs and toads—and about 90 species of reptiles,” von May said. “And considering that there are hundreds of invertebrates that potentially prey upon vertebrates, the number of possible interactions between species is huge, and we are highlighting that fact in this paper,” von May said.
In addition to the Los Amigos Biological Station, other observations were made at the Villa Carmen Biological Station, also in Peru’s Madre de Dios region, and at the Madre Selva Research Station in the Loreto region of northern Peru.
Nearly all of the sightings were made at night, when the arthropod predators are most active. During their night surveys, team members walk slowly through the forest with flashlights and headlamps, in single file, scanning the forest and listening intently.
During one of those night surveys, U-M doctoral candidate Michael Grundler and two other students “heard some scrabbling in the leaf litter.”
“We looked over and we saw a large tarantula on top of an opossum,” said Grundler, a co-author of the paper. “The opossum had already been grasped by the tarantula and was still struggling weakly at that point, but after about 30 seconds it stopped kicking.”
The tarantula was the size of a dinner plate, and the young mouse opossum was about the size of a softball. Grundler’s sister Maggie pulled out her cell phone and shot photos and some video.
Later, an opossum expert at the American Museum of Natural History confirmed they had captured the first documentation of a large mygalomorph spider preying on an opossum. The infraorder Mygalomorphae is a group of mostly heavy-bodied, stout-legged spiders that includes tarantulas.
“We were pretty ecstatic and shocked, and we couldn’t really believe what we were seeing,” Michael Grundler said. “We knew we were witnessing something pretty special, but we weren’t aware that it was the first observation until after the fact.”
A tarantula (genus Pamphobeteus) preying on a mouse opossum (genus Marmosops). Photo by Maggie Grundler, Amphibian & Reptile Conservation (amphibian-reptile-conservation.org).
Most predaceous arthropods rely on specialized body parts and venom to capture and paralyze vertebrate prey. These adaptations include modified jaws, enlarged beaks and massive fangs. Some groups have evolved dozens of venom proteins that are injected during prey capture.
Other predator-prey interactions documented in the Amphibian & Reptile Conservation paper include:
- Several examples of large spiders of the family Ctenidae preying on frogs and also a lizard. Most of the predation events documented in the paper involve spiders, and most of those were ctenids, which are commonly known as wandering spiders. Ctenid spiders are sit-and-wait predators that hunt at night and use specialized hairs on their legs to detect air vibrations and the direction of prey. Their principal eyes are responsible for object discrimination, and secondary eyes detect motion.
- A large scolopendrid centipede consuming a live Catesby’s snail-eater snake, and another centipede eating a dead coral snake that it had decapitated. “Coral snakes are very dangerous and can kill humans,” said U-M doctoral candidate and study co-author Joanna Larson. “To see one taken down by an arthropod was very surprising. Those centipedes are terrifying animals, actually.”
In addition to predation events, the researchers also report on lethal parasite infections in lowland Amazonian frogs and commensal relationships between spiders and frogs. A commensal relationship is one in which one organism benefits and the other is not harmed.
“One of the coolest things about working in Peru is the sheer number of species that you encounter every day simply by walking in the forest,” said Larson, who studies the evolution of diet in frogs. “Every day you see something new and exciting.”
“One offshoot of the work that we’ve been doing is this collection of odd natural history events we’ve witnessed involving arthropod predators and vertebrates,” she said. “I have not reached the level of being grossed out by any of it yet. We’ll see what else Peru has to offer.”
The other authors of the paper, in addition to Rabosky, von May, Michael Grundler and Larson, are Emanuele Biggi of the International League of Conservation Photographers Heidy Cárdenas and Roy Santa-Cruz of the Museo de Historia Natural de la Universidad Nacional de San Agustín, Peru M. Isabel Diaz of the Universidad Nacional de San Antonio Abad del Cusco and the Museo de Biodiversidad del Perú, both in Peru Consuelo Alarcón of John Carroll University and the Museo de Biodiversidad del Perú Valia Herrera of the Universidad Nacional Mayor de San Marcos, Peru Francesco Tomasinelli of Milan, Italy Erin P. Westeen and Maggie Grundler of the University of California, Berkeley Ciara Sánchez-Paredes of the Universidad Peruana Cayetano Heredia, Peru and Pascal Title and Alison Davis Rabosky of the U-M Museum of Zoology and the Department of Ecology and Evolutionary Biology.
The field research was supported by a fellowship from the David and Lucile Packard Foundation to Daniel Rabosky, as well as the Amazon Conservation Association, the Wildlife Conservation Society, the Rosemary Grant Award, the Edwin C. Hinsdale UMMZ Scholarship, and the University of Michigan.
Why spiders are cloaking Gippsland with stunning webs after floods
Credit: Darren Carney
Stunning photographs of vast, ghostly spider webs blanketing the flood-affected region of Gippsland in Victoria have gone viral online, prompting many to muse on the wonder of nature.
But what's going on here? Why do spiders do this after floods and does it happen everywhere?
The answer is: these webs have nothing to do with spiders trying to catch food. Spiders often use silk to move around and in this case are using long strands of web to escape from waterlogged soil.
This may seem unusual, but these are just native animals doing their thing. It's crucial you don't get out the insecticide and spray them. These spiders do important work managing pests, so by killing them off you would be increasing the risk that pests such as cockroaches and mosquitoes will get out of control.
Parts of #Gippsland are covered in #spider web. The little black dots are spiders. There is web as far as the eye can see. This is near Longford #Victoria thanks Carolyn Crossley for the video pic.twitter.com/wcAOGU9ZTu— Mim Hook (@mim_cook) June 15, 2021
Using silk to move around
What you're seeing online, or in person if you live locally, is an amazing natural phenomena but it's not really very complicated.
We are constantly surrounded by spiders, but we don't usually see them. They are hiding in the leaf litter and in the soil.
When these flood events happen, they need evacuate quickly up out of holes they live in underground. They come out en masse and use their silk to help them do that.When floods happen, spiders use silk to evacuate quickly. Credit: Darren Carney
You'll often see juvenile spiders let out a long strand of silk which is caught by the wind and lifted up. The web catches onto another object such as a tree and allows the spider to climb up.
That's how baby spiders (spiderlings!) disperse when they emerge from their egg sacs—it's called ballooning. They have to disperse as quickly as possible because they are highly cannibalistic so they need to move away from each other swiftly and find their own sites to hunt or build their webs.
That said, I doubt these webs are from baby spiders. It is more likely to be a huge number of adult spiders, of all different types, sizes and species. They're all just trying to escape the flood waters. These are definitely spiders you don't usually see above ground so they are out of their comfort zone, too.
This mass evacuation of spiders, and associated blankets of silk, is not a localised thing. It is seen in other parts of Australia and around the world after flooding.
It just goes to show how versatile spider silk can be. It's not just used for catching food, it's also used for locomotion and is even used by some spiders to lay a trail so they don't get lost.
The most important thing I need readers to know is that this is not anything to be worried about. The worst thing you could do is get out the insecticide and spray them.
These spiders are making a huge contribution to pest control and you would have major pest problems if you get rid of all the spiders. The spiders will disperse on their own very quickly. In general, spiders don't like being in close proximity to each other (or humans!) and they want to get back to their homes underground.
If you live in Gippsland, you probably don't even need to clear the webs away with a broom. There's no danger in doing so if you wish, but I am almost certain these webs will disperse on their own within days.
Until then, enjoy this natural spectacle. I wish I could come down to see them with my own eyes!
This article is republished from The Conversation under a Creative Commons license. Read the original article.