FIELD BOOK OF PONDS AND STREAMS 



Fig. 157. — Blasturus cupidus, one of the common- 

 est mayflies in early spring pools, 



I 



Family Baetinse, Blasturus. — These are the commonest 

 nymphs in the ponds through Ivlarch and late April. They 

 are chestnut brown with double leaflike gills which are similar 

 except for the last pair. They walk over the trash or swim 

 through the still water of the spring pools in which the}' con- 

 stitute the major population. They do not try to hide from 

 the light and it is easy to see hundreds of them clambering 

 or swimming heavily about in the pools. Nymphs collected 

 in February are nearly fullgrown and adults begin to emerge 

 in March. N^^mphs will live for two or three weeks in a dish 

 of water if kept fresh or supplied with aquatic plants; they 1 

 will shed their nymphal skins successfully and then fly to the 

 window-panes to rest on the glass till they cast their subimago 

 skins. 



Occurrence. — The nymphs (Fig. 157) appear in great num- 

 bers during March to April but they soon emerge and dis- 

 appear from the ponds, little ones appearing again in late fall 

 and winter. Length of fullgrown nymph half to three-quar- 

 ters of an inch. Eastern states to North Carolina and Indiana. 



Callibaetis. — CaUihcetis nymphs have three tail filaments, 

 the outer ones being fringed on one side only (Fig. 158). 



The pale green, brown-dappled Callihcetis is one of the 

 daintiest of the dwellers in newly formed pools and ponds 

 where vegetation is plentiful and carnivores are f«w (PL X). 

 Unlike most mayflies it matures in less than six weeks, and 

 there are several generations in a summer. The nymphs will 



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