HOW TO KNOW THE IMMATURE INSECTS 



9a. The 2nd pair of abdominal gills normal, not covering the remain- 

 ing pairs. Fig. 138 FamUy EPHEMERELLIDAE 



The naiads are often strikingly colored. In some 

 species the venter of abdomen forms a sucking disk. 

 They often cling to the underside of stones in swift 

 waters. 



Fig. 138. Eph«- 

 maralla sp. 



9b. The 1st pair of abdominal gills very small; 2nd pair exceptionally 

 large and covering the remaining pairs. 

 Fig. 139 Family CAENIDAE 



The naiads live in sand or mud bottoms. They ore 

 peculiar in having the second pair of gills covering 

 the succeeding pairs. The members of this family 

 are mostly of small size. 



Fig. 139. Tri- 

 corythus sp. 



10a. Claws of middle and hind legs as long as the tibiae. 



Fig. 140 FomUy AMETROPODIDAE 



There is rather wide varia- 

 tion in the naiads of the May- 

 flies. A few are even thought 

 to be predacious. They appar- 

 ently molt many times during 

 their development. They belong 

 in the eastern hemisphere 



Fig. 140. Amathropus sp. 



65 



