386 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



Family CORIXIDAE. 

 By James Francis Abbott, Ph.D. 



The Corixidae are probably the most highly specialized of the 

 Heteroptera — speaking in an evolutionary sense. The multitude 

 of variations and the apparent plasticity of the species is likewise 

 evidence of their relatively recent appearance on the earth. Repre- 

 sentatives of the family are found in all parts of the world, 

 although certain genera are restricted to various zoogeographical 

 divisions. Of the twelve genera that are recognized, seven are 

 to be found in North America, and of these three occur in 

 Connecticut. 



Corixids are to be found in shallow brooks, ponds and puddles, 

 sometimes in streams so near the sea that the water is very brack- 

 ish. They are as a rule strong flyers, and often migrate in great 

 swarms from pond to pond. At such times they not infrequently 

 come to the light. They swim through the water, back uppermost, 

 in irregular rapid jerks, and as a rule spend the greater part of 

 the time near the bottom, clinging to sticks or water-weeds. The 

 cross-barred markings of the tegmina, characteristic of nearly 

 every representative of the family, are doubtless of great value in 

 aiding the insects to escape observation, on account of the conse- 

 quent resemblance to the debris to which they cling. 



Males and females are distinguished throughout the family by 

 a number of striking morphological characters, the most remark- 

 able of which is the asymmetrical structure of the abdominal seg- 

 ments of the males. On the dorsum of the latter there is also an 

 organ of doubtful function (usually shaped like a curry-comb) 

 called the ''strigiV and the males likewise have the fore tarsi (or 

 "palae") provided with one or two rows of chitinous "pegs" or 

 teeth. By rubbing these back and forth over a roughened area on 

 the femur of the other fore-leg, a twittering sound is produced. 

 The females lack these pegs and the abdominal segments are per- 

 fectly regular. The front of the female is usually convex, that of 

 the male, concave. The eggs are usually attached to water-weeds 

 or to other debris and there are usually two or more broods in a 

 season. The following keys are based largely on male characters, 

 since the discrimination of isolated females is a matter of great 

 difficulty and in most cases is possible only when large series are 

 available for comparison. 



In order to understand the descriptions, the accompanying sketch 

 of one of our commonest species is included. See fig. 36. 



Key to Genera. 

 I. Asymmetry dextral.* First tibia not produced over pala 2 



* To the right of the observer (and of the insect) when the latter 

 is looked at from above. The intromittent organ curves toward the 

 asymmetrical side. 



