1020] Richmond, Studies on the Biology of the Aquatic Hydrophilidce 29 



which the lobes and cerci, around the terminal spiracles, spread out 

 over the surface of the water showed clearly its advanced development. 

 They are much less active out of water than the Hydrseninae but never- 

 theless move rapid. 



Hydrochous squamifer LeConte 

 Plate V . 



Egg-case. — Length of egg, 0.5 mm.; width, 0.2 mm. The case is irregular in 

 outline and varies in size but the egg is always placed towards one end of the case, 

 the two layers of silk meeting to form a flap at the other end. 



Newly Hatched Larva. — Length, 1.8-1.9 mm.; width at the thorax, 0.21-0.24 

 mm. Whitish except chitinized regions which soon darken; integument with many 

 inconspicuous setulae. Body somewhat cylindrical. 



Head strongly rounded, shorter than wide, nearly horizontal; fronto-clypeal 

 suture not visible; frontal sutures converging as far back as the middle of the head 

 but then slightly diverging and not uniting to form the epicranial suture, the frons 

 therefore concave at the sides; gula small, its posterior angles extended to form long 

 lateral arms; cervical sclerites, if present, not noticeable. 



Labro-clypeus very much reduced, the epistoma apparently at the anterior 

 margin of the head, nearly straight in front, no toothed lobe present but with a trans- 

 verse row of eight setae at the anterior margin arranged in two groups of four equi- 

 distant from the median line; area immediately behind the latter bearing numerous 

 setae mounted on minute tubercles. Lateral expansions of the epistoma not promi- 

 nent, rounded, and similar. Epipharynx with setae on small tubercles; ocular areas 

 in groups of six, oval, closely aggregated, arranged somewhat in a circle (the third 

 and fourth slightly distant.) with their longitudinal axes emanating from the center. 



Antennae fairly short, reaching only to the middle of the palpifer; first segment 

 stout, slightly concave on the inside and slightly convex on the outside, about one- 

 third longer than wide; second segment less than one-third the latter in length, 

 narrower, a little longer than wire and bearing distally a finger-like antennal appen- 

 dage in addition to the third segment; the latter not quite as long as the second seg- 

 ment and about as long as the appendage but a little wider and bearing terminal sense- 

 cones. The intersegmental membranes separating the segments are well developed 

 and allow the last two segments to be telescoped. 



Mandibles symmetrical, the anterior pieces fairly slender, only slightly tapering, 

 the tips membranous and each bearing a short recurved seta; lacinia mobilis slender 

 and bifid at the tip; a single, sharply pointed inner tooth just in front of the molar 

 area; latter setiferous. 



Maxillae with palpifer joint-like, stipes large, sides parallel, the inside with a 

 prominent swelling surmounted by a group of setae; palpifer shorter but equal in 

 width, about as long as wide, swollen, three prominent inner setae in addition to many 

 small setae mounted on minute tubercles, which cover the inside of the stipes as well; 

 palpus tapering slightly, the second segment longer than the first but shorter than the 

 thimble-like terminal segment which possesses apical sense-cones. 



