1920] Richmond, Studies on the Biology of the Aquatic Hydrophilidoe 69 



strong dorsal seta on either side of the median line, slightly anterior in position; the 

 seta at the base of the labial palpus stout and fairly prominent and those at the base 

 of the second segment slender. 



Pupa. — Length, 5.13 mm.; width at its thorax, 2.22 mm. Entirely whitish, 

 except eyes. Head smooth and bears two supraorbital styli on each side, the 

 anterior styli more lateral than in Cymbiodyta, in which they are set nearer the median 

 line than the posterior styli; an inconspicuous tubercle on each side of the median 

 line near the vertical margin. 



Pronotum smooth, its anterior margin somewhat trilobed and its posterior margin 

 straight, slightly indented just in front of the base of the elytra. The styli are 

 arranged as follows: ten on the lateral and anterior margins, two of which are on the 

 middle lobe; eight on the posterior margin counting the two corner ones; two on the 

 middle lobe just posterior and slightly lateral of the two anterior styli (these four 

 styli are more in a transverse line than in Cymbiodyta) and a transverse row of four 

 in the middle, the outer two a very little anterior the inner pairs. Mesonotum and 

 metanottmi with a transverse row of two styli. Inner spur of metatibia fairly promi- 

 nent, an outer adjacent spur less prominent. Tarsi not ending in a spine but blunt 

 and tibia? not noticeably spinous on the outer side, although the meso- and metatibise 

 have slight indications of spines. First abdominal tergite with a transverse row of 

 four styli; second to seventh tergites inclusive, with a transverse row of six styli, the 

 outer one on each side arising from a tubercle; second to seventh pleurites with a 

 stylus; eighth tergite semicircular, the rounded posterior margin bearing two styli; 

 ninth segment with a pair of tapering, fleshy cerci, a little longpr than the sixth to 

 ninth tergites together (1.2 mm.), extending caudad and very slightly diverging. 

 Xinth sternite with prominent, acute, externo-caudal angles. A pair of appendages 

 arise from between the eighth and ninth sternites and extend caudad on either side of 

 the median line to the base of the cerci and closely appressed to the ninth segment. 



Philydrus nebulosus Say 



Plate I, Figure 9 



This species is very close to P. perplexus in its early stages and the 

 egg-cases have no distinctive characteristics for their separation. From 

 thirteen egg-cases, an average of 19 larvae were obtained with 24 and 11 

 as the extremes. Eggs, laid on March 16, hatched on the 25th. They 

 seemed to feed readily on the entomostracans, Chironomidae, Tubifex, 

 etc., in the aquarium, and the first molt was noted in eight days. I 

 failed to see the second molt but on June 3 pupae were observed on 

 Cladophora, which had pushed just above the surface of the water. The 

 newly hatched larvae measured 2.256 mm. in length by 0.312 mm. The 

 inner surfaces of the anterior pieces and anterior teeth of the mandibles 

 and flap of labrum much more prominently toothed than in perplexus. 

 These latter serrations seem to keep prominent in the more mature larvae, 

 although most of the fully grown larvae are hardly distinguishable from 

 P. perplexus. 



