20 University of Michigan 



The key given above is based on IMontandon's original des- 

 criptions (Cnll. vSoc. Sci. Bucarest, xviii, p. 185. and xix, p. 

 66, 1910). 



Family Belostomatidae, the Gtant Water-bugs 



Three species of this family, belonging to two genera, have 

 been taken here, and another may occur. 



Key to the Genera of Bclostomatidac of the Douglas Lake Region 



Head not conicallj^ produced before eyes ; "furrow" of mem- 

 brane of bcmelytra sinuate ; size larger, length 40 mm. 

 or more Lethoci'KUS 



Head conically produced before eyes; "furrow" of membrane 



straight ; smaller, length less than 2^ mm Br'.LoSToM.v 



Genus Lethocekus Mavr 



22. Lctlioccnts anicricaniis (Leidy). Not at all common, 

 onl\- live adults having been secured in two seasons' collect- 

 ing, and none being reported for 1914. All the mature forms 

 were taken from the largest beach pool at Sedge Point (Sta. 

 VI), both by dredging in the mud and by running nets through 

 the vegetation. A single exuvium of a late nymjjhal instar 

 was found at Station XII on July 29, and nymphs of a Leth- 

 ocerus were fairly luunerotis in (jue of the pools at Station III 

 before this pool dried up. 



A specimen taken on the beach at Station I on July 4 was 

 determined by Mr. Torre-Bueno as Lcthoccnis obsciiriis ( Du- 

 four), but I nuist confess my inability to distinguish it from 

 L. anicricaniis. It is fully as large as several of the Douglas 

 Lake specimens of that species, measuring 49 by 18 mm., and 

 the structure of the head does not appear to be diiTerent. 



23. LctJioccriis sp. Two specimens of a Lethocerus much 

 larger than aiucrica)ius, measuring 58 mm. and 61 mm. re- 

 spectively, were taken at Station \'I on August 7 and August 



