Actually there is a Northern crayfish, at least there was a northern crayfish and it is now supposed to be called:
Virile (formerly Northern) crayfish-Oronectes virilis ( Hagen).
This Virile crayfish looks very similar to the Calico or Papershell crayfish. As you will read the range of the Virile crayfish has been extended due to accidental bait bucket introductions.
Soapbox - They should not use "accidental" bait bucket introductions. Just about every fisherman that dumps a bait bucket does it consciously and intentionally when done fishing; very rarely is it an "accident". This is why it is highly suggested that pondowners do NOT allow anglers to fish with minnows in ponds; due to "accidental" introductions of "bait". IMO The information should also include wide scale introductions across the US from fish farmers and pond stockers. If a fish farm is selling crayfish they shouild at least know what actual species they are selling. It that too much to ask? Off Soapbox.
IMO using color markings solely as way to separate crayfish is very risky business IF one is trying to get an accurate identification. Many times habitat, environment, nutrition, and genetic diversity can all influence body colors.
See the MO crayfish website for a picture of Virile which looks like a several other common crayfish across the US.
http://mdc.mo.gov/nathis/arthopo/crayfish/varcraw.htmFrom the Missouri website above for Virile crayfish it says:
""This crayfish is green-to-reddish-brown without prominent markings. The pincers are green with orange tips, and in adults are conspicuously studded with whitish knobs. Paired blotches run lengthwise along the abdomen. The rostrum has conspicuous notches or spines near its tip. This is one of our largest crayfish, with adults reaching a length of 4.8 inches or more.
The native range of the virile (“Northern”) crayfish encompasses all of the Prairie Region and a band of streams along the northern and western border of the Ozarks. Small, widely scattered populations now occur elsewhere in the Ozarks as accidental bait-bucket introductions. In the Prairie Region this crayfish is very abundant in the pools of rocky streams.
The virile crayfish is the largest of crayfish in the Prairie Region. The calico (“papershell”) crayfish differs from this species in having pincers that are gray or purple, a pale lengthwise stripe along the middle of the carapace and abdomen, and a rostrum without lateral notches or spines.""
