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42 from 1.0 to 2.0 mm in diameter. Three females were carrying from 33 to 333 1 st instar young (3mm long). Actual egg counts on the pleopods ranged from 11 to 474. The loss of eggs varied widely but, overall, averaged 28%. 79, 220 In the Maple Creek watershed of Nebraska, no females in berry were found in the fall but most were carrying eggs in the spring. They averaged 279 eggs per female which ranged from 91 to 468 and this was directly related to crayfish size. The eggs began hatching on 10 May and this continued for two to three weeks. Almost all young had left the female by the end of May. 210 The female with eggs illustrated here was collected from the upper Niobrara River on 10 May 2011. She is relatively small with a carapace length of 27 mm and was carrying 120 eggs. PRODUCTION AND GROWTH There is little variation in the size of juvenile Calico crayfish while still attached to the female through their first three molts. Their growth ceased by early September and when they were 13 to 29 mm and growth resumed about mid-April. While the aging of crayfish has been impossible up to now, it is probable that the fastest growing individuals matured at the end of their first year. Most crayfish probably did not mature until the mid-summer molt of their second year. 226 Under favorable conditions, the Calico crayfish could mature in four months after hatching, but in temporary ponds, growth would be slow and maturity would be delayed until their second year. It appears that crayfish rarely live more than two years and crayfish that matured early also died early. 19 There is high mortality of males after fall breeding and of females in the spring after their young leave. 79, 226 My collections tend to support these observations. On many occasions I have been able to collect many juveniles in an area where larger adults were almost non- existent. In Maple Creek in Nebraska, the numbers and biomass of Calico crayfish varied through the year. One site reached its peak numbers on 15 July at 40/m² and 116.4 grams/m² (this is equal to 1,036 lb/ac). Three sites that dried had peak numbers of less than half these numbers at 15 to 19 /m². The biomass figures at these three sites were also lower at 16 to 70 g/m². [15.9 g/m² is equivalent to 142 lb/acre] The early drying sites had slow crayfish growth rates and most did not mature until their second season of growth. At the one site that did not dry, young-of-the-year crayfish matured in their first season. 210 One study devised a technique to mark crayfish by clipping different sections of the abdomen so that the mark was still visible up to 16 months later. Many of these crayfish died at 12 to 18 months of age. Two years appeared to be the normal life span and only a few managed to live three years. The study sites were three large hatchery ponds which were drained often so it was possible to get direct measurements of total production. In the three years of 1939 to 1941, production in these ponds varied from 1 lb/acre to 692 lb/acre. 79