1068 FAMILY XL. — CORIXID.^E. 



paid to occur only in the muddiest of ponds, to winter as 

 adult and to fasten its eggs during June and July to the bodies 

 of crayfish, as many as 3,000 having been noted attached to 

 one of these crustaceans. The R. balanodis Abb. (1912, 118) is 

 a synonym. 



IV. Arctocorixa Wallengren, 1894, 133, 150. 



To this genus, as characterized in the key, belong the large 

 majority of our eastern species. They range in length from 3 

 to 11 mm. and have both pronotum and elytra usually marked 

 with numerous transverse alternate pale and dark lines or 

 cross-bars, their surface in part or wholly rastrate or rough- 

 ened like a file. Front of head of males usually with a large 

 concavity or impression ; in females flat or convex. As the 

 species are so numerous they are, for convenience, treated in 

 two groups, the division being based on size alone. 



KEY TO GROUPS OF EASTERN ARCTOCORIXA. 



a. Larger, length (except in nitida var. iitiiw)') 8 or more mm. 



Group I, p. 1068. 

 aa. Smaller, length less than 8 mm. GROUP II, p. 1073. 



Group I. — Arctocorixa." 



KEY TO EASTERN SPECIES OF GROUP I. ARCTOCORIXA. 



a. Pronotum without a percurrent median carina and with not more 

 than 11 transverse pale lines. 

 I>. Lineations, or pale markings of elytra, distinct and covering the 

 corium. 

 c. Palae of male narrow, oblong or strap-shaped, the pegs in a nearly 

 straight row (figs. 5 and 6). 



d. Length, 10 — 11 mm.; suture between corium and membrane con- 



colorous, the lineations continuous across both divisions; palae 

 of male strap-shaped; pegs 26 — 30. 1208. interrupta. 



dd. Length, 8 — 9 mm. ; suture between corium and membrane usually 

 marked by a yellowish line; palae of male oblong, shorter in 

 proportion to their width; pegs 21 — 24. (fig. 6). 



1209. NITIDA. 



cc. Palae of male broader, not oblong or strap-shaped. 



e. Pale bands of corium behind apex of commissure short, irregular 



in shape, giving a mottled rather than a cross-striped effect. 

 /. Pronotum more finely rastrate, crossed by ten or more dark 

 bands. 

 g. Palae of male with apex decurved, the row of pegs bent down- 

 ward (fig. 8) ; several of the pale pronotal cross lines con- 

 fluent at the ends. 1210. harrisi. 



"■Til.' .1. planifrons (Kirbyl is not Included in the key. A description of A. 

 laevigata (Uhl.), the No. 1253 of this work, was not available in time for its propel 

 placemen! In either key or text, it should follow .1. convexa (Pieb.) on p. 1072. 



