41 8 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



forms occurring in the United States are easily separated, aside 

 from the difference in habitat, as follows : 



Key to Species. 



i. Second and third joints of middle tarsi equal; female with knobbed 

 posterior pronotal process ; posterior femora incrassate in male 

 only oriander 



Second and third joints of middle tarsi unequal; female without 

 pronotal process ; posterior femora equally thick in both sexes . . 2 

 2. Third joint of posterior tarsi longer than second; hind femora 

 incrassate and spinose in both sexes ; very dark in color with a 

 more or less aeneous lustre obesa 



Second joint of posterior tarsi longer than third; hind femora 

 scarcely incrassate in both sexes, not spinose ; lead gray in color 

 (subgenus Trochopus Carpenter) ". plumbea 



R. obesa Uhler. 



Proc. Bost Soc. Nat. Hist, xiv, 107, 1871. 



This species, according to Uhler in the Standard Natural 

 History, is found throughout the Atlantic States in the rapid parts 

 of streams. In such places, the individuals congregate in schools, 

 swimming powerfully in zigzags against the current, or at times 

 sheltered behind some projecting rock, placidly paddling in the 

 eddies that swirl about it. The peculiar tarsal plume in this species 

 and its striking function are described in detail in the Canadian 

 Entomologist.* This is a difficult form to confine in an aquarium 

 as it immediately takes to diving and finally perishes. Rhagovelia 

 obesa is sometimes found winged about New York, but so rarely 

 that twenty years of collecting have yielded only seven specimens. 

 So far, it has been recorded from the Atlantic States north of 

 Georgia. It is perhaps the most widespread species of the genus 

 and it has been suspected that some of Champion's Central Ameri- 

 can species may be but unrecognized variants of it. Central 

 America seems to be the metropolis of the genus, since most of 

 the known species occur there. 

 R. oriander Parshley. 



So. Dak. State Coll. Technical Bull. No. 2, 19, ff. 2, 19, 1922. 



This species, although described from South Dakota, is inserted 

 here because our knowledge of these forms is so incomplete that 

 it or another species may be found in Connecticut. 

 R. (Trochopus) plumbea Uhler. 



Proc. Zool. Soc. London, 217, 1894. 



This species is a denizen of estuaries and bays and other 

 brackish and salt waters on our coasts. There is only one other 

 species of the genus with a like habitat, R. salina Champ., which 

 is found on the Central American coast. Nothing further seems 

 to be known of its habits, but perhaps some Floridian traveler 



* On Rhagovelia obesa Uhler, Vol. xxxix, 61, 64, 1907. 



