Triangle spiders, (Loven, 2004), are found throughout the continental United States and most of Northern Europe.
Triangle spiders mostly occupy wooded landscapes, such as forest groves, mountain terrain, and grassy plains. Populations have been discovered clustered within hollow trees and underneath rocky ledges. Commercial greenhouses have often attracted these spiders presence as well. (Loven, 2004; Nieuwenhuys and Loggen, 1997/2002)
Triangle spiders are relatively small in size, only 2 to 4 mm long. The carapace is noticeably flat, and wide to support the thick, oval shaped abdomen. A few minute bumps are apparent on the abdomen, disguised by short, stiff hairs. The coloring varies from brown to grayish, enabling these spiders to blend with the environment. (Gertsch and Willis, 1979; Patent and Hinshaw, 1980)was once believed to have only six eyes due to dense hair coverage of the other two. Males, although smaller in size than females, bear a close resemblance.
Males reach maturity in the early fall. Before searching for a mate, a male must first charge his reproductive organ with sperm. He does this by constructing a web, on which he deposits semen from the rear genital opening. Hanging from the web frame, he uses his legs to pull the web strand closer and draw the semen into his claw-like palp.
Having extremely small eyes, a male must rely on recognition of a female's cribellate silk dragline to track her. Females coat their silk with a sexual scent (pheremone) which attracts males. Since triangle spiders are short-sighted, vibrations sent along the web are the primary means of courtship.
When mating begins, the male inserts the embolus spur on the tip of his palp into the female's reproductive structure (epigyne). The female's resevoir absorbs the flow of sperm, where it will be stored until her eggs are ready for fertilization.
After her eggs develop within the ovaries, they are ready to be laid. First, the female weaves a woolly sheet of silk on which to deposit her eggs. As the eggs are laid, she covers them with a sticky substance containing the male's sperm. The permeable lining of the eggs allows sperm in to complete fertilization. Continuing to wrap the eggs in silk, she creates a protective egg sac. The elongated sacs are then strung across the triangular web in a row, where she aligns her body to blend with them. Within the sac, the postembryo soon disgards its outer covering (integument) and emerges a first-instar spiderling. (Nieuwenhuys and Loggen, 1997/2002; Preston-Mafham, 1991)
Triangle spiders receive their common name from the unusual web members of the species weave. Unlike other web weavers, the Uloboridae, posesses no venom glands, and therefore does not bite its victims to kill them. Triangle spiders usually practice solitary hunting/trapping skills. However, webs have been found woven together in large social groups within the environment. (Nieuwenhuys and Loggen, 1997/2002)web is not constructed in a circular pattern (orb), but rather as a triangle. These spiders use this unique web design to capture and ensnare prey by collapsing the web on the insects and immobilizing them with silk. A species from the fmaily
Triangle spiders, unlike most spiders, have no venom glands. For this reason they must rely solely on web weaving abilities for prey capture. Targeted prey usually include small flying insects, such as flies and moths. These insectivores use triangular webs as a snare to catch and entangle victims. By forming a Y-shaped framework with four attached radii between twigs or tree branches, these spiders can construct their triangluar webs. Triangle spiders then position themselves, outstretched along the frame of the web, holding back any slack with their legs. As an insect flies into the web, the spider tightens and releases excess slack to entangle the insect within the woolly (cribellate) silk strands. If the insect struggles, (Patent and Hinshaw, 1980; Preston-Mafham, 1991; Preston-Mafham, et al., 1984)will turn its back and use its spinnerets to wrap the insect with a thick, blueish silk until the prey is completely shrouded. Once the prey has been immobilized, the spider uses its jaw mechanism to break apart its body, while the maxillary glands secrete powerful digestive enzymes to break down the internal organs. Finally, is able to harvest the liquified protein of its meal by using its sucking stomach.
The webs of a triangle spiders may have zig-zags (stabilimentum) running across them. This pattern is a result of the spider's vibrations from walking on the web. It is thought to blur the outline of its web, gaurding against detection by predators and potential prey. (Loven, 2004; Zschokke, 2000)
Nancy Shefferly (editor), Animal Diversity Web.
Michelle Smith (author), Fresno City College, Carl Johansson (editor), Fresno City College.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
fertilization takes place outside the female's body
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly insects or spiders.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
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Loven, N. 2004. "Nick's Spiders of Britain and Europe" (On-line). Accessed February 16, 2005 at http://www.nicksspiders.com/nicksspiders/index.htm.
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Preston-Mafham, R. 1991. Book of Spiders and Scorpions. London, England: Quarto.
Preston-Mafham, , Rod, Ken. 1984. Spiders of the World. New York,NY: Facts on File, Inc..
Zschokke, S. 2000. "Web Construction Gallery" (On-line). Accessed February 21, 2001 at http://pages.unibas.ch/dib/nlu/staff/sz/spidergallery.html.