70 THE CANADIAN ENTOMOLOGIST. 



A STUDY OF HYDROMETRA LINEATA. 



BY J. O. MARTIN, CORNELL UNIVERSITY, ITHACA, N. Y. 



Among the reeds and rushes that border quiet streams and ponds 

 lives Hydrometra lifieata, one of the least known of our North American 

 Hemiptera. This insect is comparatively rare in collections, but common 

 enough in nature, though owing to its small size and inconspicuous 

 appearance it escapes all but the sharpest-eyed collectors. Its elongate 

 body is borne on hairlike legs and resembles a bit of twig or grass more 

 than a living insect. After the eye becomes accustomed to the odd 

 shape, they are most easily distinguished, especially when they move 

 about over the surface of the water. During the past summer I took 

 over five hundred specimens of this insect without any special effort, 

 finding them common through New York .State, Massachusetts, and 

 Connecticut. 



The appearance of this insect is unique and exceedingly grotesque, 

 for the head, thorax and abdomen are so elongate and the legs so thin 

 that it produces the effect of a minute Indian club stalking about on the 

 water. Closer examination reveals a pair of solemn, protruding eyes 

 situated at about the middle and on either side of the handle of this 

 Indian club, while from the end a pair of threadlike antennae are waved 

 about in a mysteriously cautious manner. Underneath the head is the 

 murderous beak, the common possession of all hemipterous insects. In 

 very rare cases individuals may be found with a pair of wings closely 

 folded upon the back and covered with leathery hemelytra, which are only 

 to be detected by the use of a lens. 



The economy of this elongate form becomes at once apparent on 

 studying the habits of Hydrometra. In the first place, it reduces the 

 insect's weight to the minimum and lessens the liability of breaking 

 through the treacherous surface film upon which the life of this aquatic 

 pedestrian is passed. In the second place, the long, cylindrical body is 

 so like a bit of twig in appearance that Hydrometra is protected from his 

 enemies and concealed from his prey, which do not in the least suspect 

 in this apparent straw the presence of a deadly foe. 



The genus Hydrometra was first established by Latreille in his 

 "Precis des Characteres Generiques des Insects" (1797) p- 86. 1 have 

 not had access to this book, but in his '■ Histoire Naturelle des Crustaces 

 et Insects," T. xi., pp. 267-269 (1804), Latreille says : " I have taken 

 the characters of the insect pointed out by Ceoffery, Cimex stagnorum 



