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Recognizing
Spider Groups
by John Jackman
Spiders can be identified using a variety of characteristics.
The first separation to infraorder is based on the position of the
chelicerae. If the chelicerae are pointed forward then they fall into the
Megalomorphae. These spiders all are large, husky spiders which includes
mostly the tarantulas. All of the other spiders have the chelicerae
pointing downward at least somewhat and are in the infraorder
Araneomorphae. Most of our spiders are in this infraorder.
Spider identification to family is based on a variety of
characters which includes: number of eyes, arrangement of the eyes, eye
size, shape of the body segments, hairs on the legs, number of claws on
the feet and various other characters. Sometimes short cuts can be used to
identify spiders to family. For example, if it makes an orb web it should
be in one of these families: Araneidae, Tetragnathidae, Uloboridae, or
Linyphiidae.
Another short cut is the use of the egg sacs. Lycosidae carry
egg sacs under the abdomen in their spinnerets. A few families like
Scytodidae and some Pholcidae carry eggs in their chelicerae.
Identification to species gets quite tedious. You need full
grown adult specimens to get a good identification. Genitalia of males and
females should be compared to scientific illustrations of the individual
species to confirm the identification. Male genitalia are on the end of
the pedipalps which appear swollen. The structures there are complex
plates and membranes which fit into the female during mating. The female
genitalia are found on the underside of the abdomen. Of course some
species can be easily recognized at a glance but many need that serious
level of attention to confirm the identification.