194 THE UNIVERSITY SCIENCE BULLETIN. 



Color. Dorsal color greyish white, eyes red, margin of abdomen and 

 limbs pale testaceous banded with dull smoky brown or black. 



Venter. Hairs dull black, beak and part of frons very dark smoky, as 

 are the antennas, which are directed downward. Coxse, trochanters and 

 femora dark, fore and middle tibiae dusky, hind tibia darkest in middle, 

 distal end light. Tarsi all dusky, with broad transverse median band of 

 testaceous. The color marking of hind leg is distinct. The outer one- 

 third of tibia pale, rest of segment smoky testaceous. Tarsus very dark 

 smoky, almost black, with a wide transverse pale band occupying more 

 than one-third of the segment. This leaves both ends of segment dark. 



Structural Peculiarities. No ventral abdominal median carina present. 

 Distinguished from other first instar nymphs by table given under A^. 

 irrorata. 



Biology of Bnenoa margaritacea Bueno. 



So far as the writer knows, there has not been an account of the 

 biology of any species of either this genus or Anisops, its near relative, 

 aside from his own notes published in the Entomological Nervs in 1917. 

 In this paper he presented some observations on Buenoa. margaritacea 

 Bueno. This is a slender silvery backswimmer, more or less of pink 

 showing upon the dorsum of the thorax. The venter of the abdomen is a 

 deep red in living specimens. This darkens in museum material, and has 

 led to the error of the description in calling it black. Uhler said that 

 Anisoqjs platijcnemis preferred the cold spring water in Maryland where 

 he had taken it late in October after the frosts had set in. Bueno notes 

 that it prefers the more open waters, and the writer has found it in 

 muddy ponds in Kansas where it floats submerged in open water. 



Oviposition. Attempts to secure eggs of this bug failed until exami- 

 nation of the ovipositor made it apparent that the eggs were hidden in 

 plant tissues. They were then found in floating plants in the pond, and 

 secured in the aquarium by providing cattail leaves and smartweed stems. 

 One uprooted smartweed plant, floating in the Smith pond, was almost 

 riddled with oviposition incisions. Not only were the stems swollen and 

 distorted by the many eggs they contained, but the leaves were employed 

 as nidi with varying degrees of success. The leaves were punctured, and 

 the egg, when present, rested suspended beneath, attached by the collar 

 shown in the drawing on plate XXIV, to the upper surface margins of the 

 incision. The many perforations or slits through the leaves gave their 

 testimony to the many failures in attempting to employ so thin a struc- 

 ture for nidification. The eggs are placed in the plant tissue with one 

 bit of surface exposed. 



Number of Instars. There are five nymphal instars, and the duration 

 of the various stages is much the same as in other back-swimmers. 

 Adults are to be taken from early spring to late fall. About the middle 

 of June they are most abundant in all stages of development. 



Food Habits. One striking point in their biology is the adaptation of 

 their two slender anterior pairs of limbs to food getting. The food of 

 these insects consists of the small entomostracan Crustacea, and the four 

 anterior limbs are margined with rather long spines which form when 



