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41 location increased 10 to 20-fold after dark. Juveniles, on the other hand, were active both day and night until the autumn of their first year. Females with attached eggs or young usually stayed in seclusion, even at night. 226 Crayfishes are a favorite prey of many species so refuges are important. Calico crayfish avoided overly large refuges but also did not select for the smallest refuge that they could fit in. Actual measurements of chosen refuges showed they picked one between 1.4 and 2.3 times their carapace width. Individuals also tended to select the same size refuge in successive trials. This says that population sizes could be affected by the availability (or shortage) of refuges. 68 When temperature preferences were tested, Calico crayfish avoided temperature extremes (6C and 36C) but they wandered freely through the intermediate temperatures. They were most active at night where they tended to select a temperature around 22C while, during the day, they were inactive and selected areas with a temperature around 4 degrees cooler. 34 It was noted above that the Calico crayfish preferred a rock substrate over mud if they had that choice. But, when both the Northern crayfish and Calico crayfish were in the same tank, the Calico crayfish were on the mud and few on the rock. This was because the Northern crayfish were more aggressive and more successful at evicting Calico crayfish from preferred rock crevices. So, because of this, in streams with rocky, flowing water and stagnant, muddy water, the Calico crayfish will be found in the muddy areas. 15 In a twist in Germany, one exotic crayfish, the Calico crayfish, was replacing another exotic, the Spinycheek crayfish (Orconectes limosus). The Calico was more aggressive and was often successful at displacing the Spiny cheek crayfish from preferred habitat. Here we have one introduced species displacing another. 26 When the Calico crayfish's ability to maintain itself in a current was tested, they started to slip downstream when it got over 26 cm/sec (0.85 ft/sec). This is quite low and might help to explain why they are mostly found in quiet waters. 153 REPRODUCTION Mating in the Calico crayfish can occur whenever the males are in breeding form and runs from mid-June to mid-October with a peak in late summer. In early fall, the females enter their burrows for the winter. The time of egg laying isn't really known but is probably in the spring before they emerge. A few females had laid eggs in the fall, but this was rare. 79, 226 Egg counts for 37 first spawn females averaged 84 and ranged from 4 to 170. Second spawn females averaged 195 (range of 38 to 289). 226 In Indiana streams, 15 females collected in early April were carrying from 33 to 367 eggs which ranged