1920] Richmond, Studies on the Biology of the Aquatic Hydrophilidee 55 



not as long as thorax is wide. First six segments of the abdomen about the same width 

 as each other and slightly wider than the mesothorax. The scutella are more distinct. 

 Seventh to eighth segments narrowed caudally. Small round patches composed of 

 tapering seta? are present on the folds as follows : six on the anterior scutal fold, the 

 two inner ones almost contiguous; three on the posterior scutal fold; four on the 

 scutellum; and four on the intersegmental membrane. The pleural lobes also bear 

 groups of these setae in addition to the brown setae. 



Hydrobius fuscipes Linnaeus 

 Plate I, Figures 3 and 8 



In the early spring fuscipes is very abundant but, as the season pro- 

 gresses, they are harder to locate. Many have been taken under lights 

 at night and they take flight very readily. Thus their apparent absence 

 from their normal habitat is doubtless accounted for. This absence is 

 evidently only periodic, as they are sometimes quite abundant in the 

 middle of July when the pools are becoming concentrated. Miall says 

 that many pupse of fuscipes are found during July and that the globular 

 cell is formed one-half an inch below ground in mud or clay on the bank. 

 He adds that the adults appear in August and soon lay their eggs. 



No constant differences could be found between the larva of this 

 species and globosus. H. fuscipes is often a little smaller but otherwise 

 they are apparently identical. No specimens of full-grown larvae are at 

 hand ; but I would not expect striking differences in them. The middle 

 tooth of the labro-clypeus seems to be constantly truncate in the speci- 

 mens of' fuscipes which were examined, but T hesitate to consider this as 

 a separation character. 



Hydrobius tesselatus Ziegler 



A full-grown larva of this species was taken, together with the 

 adult, by Mr. E. A. Schwarz. It was found among some leaves which 

 had caught in the tree-roots near the bank of a swiftly flowing stream. 

 The larva closely resembles globosus and is quite tuber culate. 



Hydrobius scabrosus Horn 



All the stages, except the egg-case, are in the U. S. National Mu- 

 seum Collection. They were taken September, 1891, in debris in a 

 stream at Bear Creek, Montana. The larva looks very much like a small 

 globosus larva. It differs, however, in the teeth of the labro-clypeus. 

 The full-grown specimen has only four distinct teeth, three to the right 

 and a fourth set a little to the left of the three. The middle tooth of the 



