FIELD BOOK OF PONDS AND STREAMS 



7. Claws of at least front tarsi distinctly ante-apical, with 



terminal tarsal segment more or less cleft. 8 



Claws all apical, last tarsal segment entire. 9 



8. Hind femur extending beyond apex of abdomen; in- 



termediate and hind pairs of legs approximated, very 

 distant from front pair. Beak 4-segmented. 



Water striders, Gerridce, p. 230 

 Hind femur not extending much beyond apex of abdo- 

 men; intermediate pair of legs about equidistant from 

 front and hind pairs (except in Rhagovelia) ; beak 3- 

 segmented. 



Broad-shouldered water striders, VeliidcB, p, 229 



9. Antennee 4-segmented. Membrane of wing without 



cells. Mesoveliids, MesoveliidcB (not included) 



Water-measurers, Family Hydrometridae. — These bugs are 

 concrete examples of slendemess and deliberation. They 

 have long thin bodies, spindly legs, and long, elbowed- 

 antennas and their heads are as long as the whole thorax, 

 which is by no means short (Fig. 171). They walk over 

 dead reeds at the margin of ponds, or on duckweed and lily 

 leaves, and even on the surface film, always seeming to mea- 

 sure each step as they go. Sometimes they are found on 

 sphagnum moss on the edges of bog ponds, one of the generic 

 names in the group being Limnobates, which means "marsh- 

 treader." 



Water-measurer, Hydrometra martini. — These water- 

 measurers (Fig. 171) are the most widely distributed of the 



Fig. 171. — Water-measurer, Hydrometra martini, 



228 



