Occasional Papers of the Museum of Zoology 21 



10, 1918. The smaller one especially is very distinct from 

 auicricanus, and this appears to be an undescribed species, but 

 more material is needed to decide its status definitely. Mr. 

 Torre-Bueno writes me, "The large Lethocerus is one that I 

 have received from the west — Oregon, Washington, etc." 



Genus Belostoma Latreillk 



24. Bclostoma fliiminemn Say. Common all summer in all 

 the pools and bogs where there was submerged or emergent 

 vegetation growing in shallow water. Males which were car- 

 rying eggs were often seen in July. 



Family Corixidae:, the Water Boatmen 



Representatives of two genera of this family have been 

 found at Douglas Lake. The following key will serve to dis- 

 tinguish them. The strigil in Arctocorixa is a small but dis- 

 tinct elongate or elliptical plate at the dextral margin of the 

 antepenultimate tergite of the abdomen, and in our species at 

 least, is directed longitudinally or obliquely. 



Strigil absent; basal segment of hind tarsi with a large apical 



black spot Callicorixa 



Strigil present in males ; basal segment of hind tarsi without an 

 apical black spot, although sometimes fringed with black 

 hairs Arctocorixa 



Genus Callicorixa B. White 



25. Callicorixa sp. Three specimens of a Callicorixa, prob- 

 ably C. kollarii (Feiber), were taken in the Maple River be- 

 low Station VIII on Atigust 17, 1914. No others have been 

 collected in the region. 



Genus Arctocorixa WallEngren 



Several specimens of the 1913 collection were sent to Pro- 

 fessor Abbott in that year, and he identified them as belong- 



