282 A NATURALIST IN THE GREAT LAKES REGION 



Dromogomphus and Gomphns has its sides parallel. Of the two 

 latter the first has acute, spiny-tipped dorsal hooks on the 

 abdominal segments, while in Gomphiis such hooks are usually 



s^W"^- 



■4,V^*": 



*r? 





%>^ 



Fig. 428. — Red-bellied dace, Chrosomiis erythrogaster 



absent and are always dull. Family Cordulegasteridae includes 

 only the genus Cordulegaster. The rest are therefore included 



Fig. 429. — Blunt-nosed minnow, Pimephales notatus 



in family Lihellulidae, the nymphs of some of w^hich are not 

 sufficiently wxll known to make accurate determination possible. 

 If there is a pyramidal 

 horn on the front of 

 the head and a small 

 dorsal hook on seg- 

 ment ten, the nymph 

 is of the genus Ma- 

 cromia. If the head 



Fig. 430. — Johnny darter, Boleosoma nigrum 



bears a tubercle on each side and segments three to nine bear 

 dorsal hooks, the nymph is that of Epicordidia. If the lateral 



