hungerford: aquatic hemiptera. 91 



three together, the outer third tapering asymmetrically to tip. Limbs are 

 stout, and tarsi one-segmented, ending in two apical claws. A single 

 dorsal pore on the anterior margin in the median line of the fourth ab- 

 dominal segment. 



Morphological studies. Aside from the external structures studied by 

 taxonomists, no morphological work has come to the attention of the 

 writer. 



Family HYDROMETRID^ Billb. 1820. 



Limnobatidw Fieb. 1851. 



A. Taxonomy of Hydrometrid^. 



Family Characteristics. Exceedingly slender bugs of a dark color that 

 dwell upon the shores and floating vegetation of the water. The adults 

 are dimorphic in respect to wings. The apterous forms are perhaps more 

 common than the winged, especially in the north. The head is as long as 

 the entire thorax, though it too is elongate. Ocelli absent; eyes distant 

 from the anterior margin of the thorax; antennae four segmented, fili- 

 form ; rostrum three segmented ; tarsi three segmented. One genus and 

 two species in America. At least a dozen species in the world. 



Historical Revietv. Since the genus Hydrometra was established in 

 1801, these strange bugs have been known best, in this country at least, 

 by the name of Limnobates, which translated into English means marsh- 

 treaders. This name was assigned to them by Burmeister in 1835. Most 

 of the European notes deal with the species H. stagnorum. Long before 

 this time, however, we can identify these insects in the literature. Swam- 

 merdam 1737 (Hill's Trans. 1758), in speaking of "water Tipula," 

 which he says are worthy of the greatest attention, on account of the 

 wonderful lightness wherewith they run on the surface of the water," 

 mentions a species of this insect, which is "of a wonderful delicacy and 

 of a very singular structure and very slow paced." This, I take it, is 

 Hydrometra. De Geer, 1752, figures a Hydrometrid under the name of 

 Cimex acus, while Geoffrey calls it "La Punaise aiguille." It is indeed 

 slender like a needle. Linnaeus placed the then known form stagnorum, 

 which he described, in the genus Cimex. Lamarck is credited by Van 

 Duzee with the generic name of Hydrometra, 1801. 



Genus HYDROMETRA, Lam. 



Sufficiently characterized by the family description for the present. 

 Two species are listed for this country. They may be separated by the 

 following characters taken from the writings of Kirkaldy and Bueno. 



KEY TO HYDROMETRA. 



A. Terminal segment of male (from above abruptly enlarged at tip and 



bearing a well-marked spiniferous tubercle. Caudal margin of this 



genital segment sinuate in lateral views. H. martini Kirk. 



AA. Terminal segment of male (from above) swollen in outer half but 



not abruptly so. Spiniferous tubercle lacking or not prominent. 



H. australis Say. 



