38 Bulletin American Museum of Natural History [Vol. XLII 



verse folds while the intersegmental membrane has only one; sternites with similar 

 arrangement except that there is a longitudinal fold on each side of the three trans- 

 verse folds and a fourth indistinct transverse fold was observed in some specimens. 

 The bifore spiracles at the tip of small tubercles. Both the epipleurite and hypo- 

 pleurite bear a tubercle. The transverse row of tubercles is lacking on the second 

 fold of the sternite but a single prominent tubercle is present on each side of the 

 third fold as well as one behind the middle of the longitudinal fold. 



The- eighth tergite represents the superior valve of the stigmatic atrium and 

 bears a large, shield-shaped, chitinous plate, which is slightly emarginate at the 

 middle of its anterior border but more prominently so just behind the two middle 

 lobes of the caudal margin of the eighth tergite. The structure of the atrium is very 

 close to that of Hydrophilus. It differs from the latter principally by the fact that 

 the two middle lobes of the hind margin of the superior valve are more distinct 

 resembling the mesocerci and that the two anterior setae of the plate in front of the 

 cerci are set farther apart. The median lobe of the ninth tergite with two distal setae. 

 The prostyles are short, not exceeding the sides of the body, broad, rounded, and 

 depressed. 



Full-grown Larva. — Length, 14 mm.; width at the thorax, 3.2 mm. General 

 color brownish above and dirty white below; chitinized regions reddish brown. Head 

 dorsally with a yellow stripe on each side; ventrally with a median and two lateral 

 pairs of yellow stripes; measures 2 mm. in width and 1.44 mm. along the mid-dorsal 

 line. First segment of antenna longer in proportion than in the first instar, more 

 than four times the second segment. Labro-clypeus nearly straight, often slightly 

 crenate, and some specimens retain the most lateral tooth of the first instar on each 

 side, but it is very inconspicuous. Mandibles with the outer spur of bifid inner tooth 

 lacking. Lobe of palpifer very much reduced; dorsal setae of mentum (about four- 

 teen) arranged somewhat in a transverse elipse; externo-frontal angles rounded but 

 prominent and with a small outer seta; tubercles of abdomen prominent and each 

 bearing a group of long, slender, terminal setae. 



Pupa. — Length, 12 mm. (curled up); width at its thorax, 5.6 mm. Entirely 

 whitish except reddish brown eyes. 1 Head smooth, no supraorbital seta?, oval, raised 

 areas on each side of the epicranical suture near the vertex very small. Pronotum 

 smooth with middle lobes not prominent. Motory styli are long, fleshy and annulate, 

 each bearing a terminal seta, slightly recurved and arranged as follows: three in a 

 transverse row on each side near the anterior margin; four in the middle just back 

 of the anterior margin, the two inner ones set back a little; six in a transverse row at 

 the posterior margin (no corner styli) ; two on the basal half of each side; and two in 

 a transverse row across the middle. Meso- and metanotum with a pair of transverse 

 styli; scutellum well marked; metasternal spine long. Inner spur of metatibia very 

 prominent. Tarsi not ending in prominent spines nor tibiae spinous on the outer 

 side. Metathoracic pterotheca visible from above. First to seventh tergites with a 

 transverse row of four styli, second to seventh pleurites each with a stylus. Eighth 

 tergite with two very small indistinct lobes at its posterior margin on each side of the 

 median line and each bearing small stylus. Ninth segment terminating in two crooked, 

 fleshy, superficially annulate cerci aboug 1.45 mm. long. Cerci diverge as far as their 



1 A fresh pupa showed the eyes entirely white except the six pigment-spots of the ocular areas, which 

 were grouped at hind margin of the head. 



