. Bulletin. Natural history; Natural history. August 1985 Crayfishes and Shrimps of Illinois 345 of streams more often than do the species just mentioned, perhaps to forage as well as to mate, but do so more frequently during the mating and egg- and young-carrying seasons. Freshwater Shrimp Life Cycle Females carry eggs attached to their pleopods between April and August in Illinois and between February and October farther south. The eggs hatch, and free-swimming larvae pass through six stages in about 3 weeks, described in detail for Palaemonetes kadiakensis by Broad &: Hubschman (1963).
. Bulletin. Natural history; Natural history. August 1985 Crayfishes and Shrimps of Illinois 345 of streams more often than do the species just mentioned, perhaps to forage as well as to mate, but do so more frequently during the mating and egg- and young-carrying seasons. Freshwater Shrimp Life Cycle Females carry eggs attached to their pleopods between April and August in Illinois and between February and October farther south. The eggs hatch, and free-swimming larvae pass through six stages in about 3 weeks, described in detail for Palaemonetes kadiakensis by Broad &: Hubschman (1963). Larvae and juveniles increase, and adults de- crease, in abundance through the sum- mer. Adults disappear in late summer- early fall, corresponding to a maximum life span of about 1 year in Palaemo- netes kadiakensis and 2 years in Macro- brachium ohione. The largest adults mature and reproduce earliest in the year. Observations on copulation ap- parently are unrecorded. KEY TO ILLINOIS SPECIES Morphological characteristics used shrimps in keys and systematic accounts to describe and identify crayfishes and are illustrated in Fig. cephalic process central projection caudal process mesial process A central projectioi mesial process B. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Illinois. Natural History Survey Division. Urbana, State of Illinois, Dept. of Registration and Education, Natural History Survey Division
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