. Bulletin. Natural history; Natural history. 344 Illinois Natural History Survey Bulletin Vol. 33, An. 4. Fig. 5.—Female Orconectes immunis with eggs attached ("in berry"). into the glair from the anmilus ventrahs and external openings of the oviducts, respectively. Following oviposition, the glair hardens and cements the fer- tilized eggs to the pleopods. With eggs attached to her abdomen, a female cray- fish is said to be ovigerous or "in berry" (Fig. 5). Eggs are carried by the female for 2-20 weeks, depending on the water temperature. When the eggs hatch, the young rem
. Bulletin. Natural history; Natural history. 344 Illinois Natural History Survey Bulletin Vol. 33, An. 4. Fig. 5.—Female Orconectes immunis with eggs attached ("in berry"). into the glair from the anmilus ventrahs and external openings of the oviducts, respectively. Following oviposition, the glair hardens and cements the fer- tilized eggs to the pleopods. With eggs attached to her abdomen, a female cray- fish is said to be ovigerous or "in berry" (Fig. 5). Eggs are carried by the female for 2-20 weeks, depending on the water temperature. When the eggs hatch, the young remain attached to the abdomen and are carried by the female througfi three instars. The first juvenile instar has extremely large eyes, a yolk-filled carapace, an incomplete abdomen, and hooked chelae. First instars attach to the female with the hooked chelae and by a stalk linking the telson of the instar to the abdomen of the mother. After 2-7 days first instars molt to second instars, which are more adultlike but still lack a fully developed abdomen and cling to the mother's abdomen by their chelae. After another 4-12 days, another molt results in the third instar, which closely resembles the adidt and hangs onto the mother with its chelae and pcreiopods. It may leave the protec- tion of the mother for short periods. Subsequent instars are free living. Growth proceeds through a series of (i-10 molls during the summer, and sexual maturity may be attained by late summer or early fall. Sexual matu- rity in the male corresponds to a molt to form I. The first molt following the mating period returns the male to a nonieproducti\e state (form II) in which the gonopods are without cor- neous tips. Following copulation, females do not molt until after the young permanently have left. In Illi- nois, crayfishes appear to survive a maximum of two reproductive seasons. In nonburrowing Illinois crayfishes, all aspects of their life history occur in surface waters. Burrowing species spend
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