106 



THE UNIVERSITY SCIENCE BULLETIN. 



Following is given a table of measurements of the various instars and 

 of the adults : 



Summary. Mesovelia mulsanti is found about the margins of ponds 

 and pools upon floating vegetation where it feeds upon small organisms 

 coming to the surface film from below or that fall upon it. The species 

 probably passes the vdnter as adults that begin ovipositing in the spring. 

 They place their eggs in the stems of plants and even in the spongy wood 

 of floating logs. There is a succession of generations throughout the 

 season, each cycle requiring about 24 days. Winged and wingless forms 

 occur together. Besides flying from pool to pool, they may be transferred 

 in the egg stage. Mr. Beamer sent them from the southern part of the 

 state to the writer at Lawrence, Kan., in the stems of sedge used as 

 packing for some Naucorids. 



The general distribution of this species, and the ease with which it may 

 be controlled and observed both as to oviposition and to hatching, make it 

 a valuable object for studies on many phases of animal behavior. 



Family GERRID^. Am. & Serv. 1843. 



Aniyot and Serville, Hemip. pp. 1, 410, Groups Gerrides. 



A. Taxonomy of Gerrid^e. 



Family Characteristics. Long-limbed bugs that live upon the water. 

 The antennae are longer than the head and exposed, 4-segmented. The 

 head is shorter than the thorax including the scutellum. The limbs are 

 slender, the tarsi covered by close set pile and the claws of at least 

 the front pair distinctly anteapical with the terminal tarsal segment 

 more or less cleft. The hind femora extend beyond the tip of the 

 abdomen; the intermediate and hind pairs of legs approximated, very 

 distant from front pair; ocelli present, but sometimes very obscure; eyes 

 close to the anterior margin of prothorax. Roj;trum 4-segmented, first 

 and second segments short; tarsi 2-segmented; parts of hemelytra more 

 or less confluent, often wingless. 



Historical Review. The name Gerris was so promiscuously used for 

 various bugs by the early writers that Stal thought to help matters by 

 substituting other names. So many of us have known these bugs as 

 Hydrohatidse. It may be of interest to note that the name Tijmla now in 



