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56 growth in summer can make them as black as tar. The key identification character of the species is the shape of the first pleopod of a Form I male. The central projection is corneous, dark yellow and slightly curved (upper photo). The mesial process diverges from the central projection and may be slightly spatulate on the end. In non-breeding season the pleopod reverts to a juvenile form (Form II) that is of little use for identification (lower photo). The rostrum of the Northern crayfish tapers with a dished center with strong ridges on both sides. There is a fairly sharp tip and no median carina. Juveniles have much more pronounced spines on the tip and on each side. These side spines get very small as they get older. The aureola in the Northern crayfish is very narrow but the two halves never overlap or touch. The chelae or claws of the Northern crayfish are large and strong with an olive color though this can vary. The tubercles are light tan and the very tips of the fingers are also light. Dead, dried out chela are often a bright blue. The movable finger (dactyl) has a double curve. Setae are almost always present between the fingers but can vary from a tiny amount in the angle like this specimen to so much that it totally fills the gap. There are no keys that will work to identify female crayfish. They are identified by their association with and similarity to male crayfish collected from the same location. That is because the main sex characteristic, the annulus ventralis, (the urogenital pore), is very similar between species. Now, given that, since we only have six species of crayfish in the state of Nebraska, the secondary characteristics noted above will often work with females as will the annulus ventralis. These photos illustrate the