Amphipoda
Small Water Shrimps
Humpbacked, many-legged crustaceans, [fig. 69], that are, unlike the isopods, flattened from side to side like the fleas. They are all aquatic but are seldom found swimming in open water; they prefer to live in tangled masses of vegetation, under stones or logs, and among debris in the very shallow water where it touches the bank. These little shrimps are never more than about one-half inch long and are frequently collected in large numbers along with aquatic beetles. As is the case with the aquatic sowbugs, certain species of amphipod shrimps occur in subterranean water sources and frequently are found in wells. Most of these species are blind.
Fig. 69.—Amphipoda. Gammarus sp., a common small water shrimp. Actual length 0.4 inch.
Fig. 70.—Scorpionida. Centruroides vittatus, the only scorpion known to occur in Illinois. Actual length 2.0 inches. (Drawing by Alice Ann Prickett.)
Scorpionida
Scorpions
Animals belonging to the spider group; characterized by a pair of stout pincers at the end of each front leg and a long tail-like extension of the abdomen ending in a sharp sting, as in Centruroides vittatus (Say), [fig. 70]. They have fairly long bodies and five pairs of legs each, including the chelate pair. During the day they live under stones and bark, moving about at night in search of insects and other small organisms on which they prey. Many species occur in the Southwest; the range of one of these extends as far northeastward as southwestern Illinois.
Pseudoscorpionida
Pseudoscorpions
Animals belonging to the spider group; characterized by a pair of stout pincers at the end of the front legs, as in Larca granulata (Banks), [fig. 71]. They have short, stout bodies, each with five pairs of legs including the chelate front pair, but unlike the true scorpions they have no tails or stings. The pseudoscorpions are sometimes found indoors in old books, looking for their prey of small insects. They occur in greater numbers in wooded areas.