46 Bulletin American Museum of Natural History [Vol. XLII 



Legs fairly long, with tibise nearly as long as, but a little more slender than, the 

 femora ; femora shorter than the small coxae ; tarsi well developed, claw-like, almost 

 as long as th e tibise, with two inner setae one distal to. the other. 



Abdomen with eight prominent segments, slightly narrowed caudally, ninth and 

 tenth rudimentary. The first seven similar, each with two very much reduced, oval, 

 chitinized patches on the praescutum near the cephalic margin on each side of the 

 median line, and four prominent tubercles in a transverse line across the posterior 

 fold of the scutum, each bearing a seta. Each tergite seems to consist of a prsescutum, 

 scutum divided into two transverse folds and posteriorly a very narrow scutellar fold 

 that continues to the spiracular part of the tergite ; sternites have similar correspond- 

 ing folds. The eighth tergite represents the superior valve of the stigmatic atrium, 

 bears a large chitinous plate, 1 which is about as broad as long. The caudal border 

 of the valve is chitinized in part, possesses setae and presents a bilobed appearance. 

 Procercus one-segmented, 2 subcorneal with a chitinous band on the inside and a 

 group of three setse arising dorsally from tubercles on the apical half. Mesocercus 

 two-segmented and chitinous, the first segment elongate, dome-shaped, bearing a 

 central dorsal seta; the second very small, papilliform, and bearing a terminal seta. 

 Between these two segments in the membrane there are several sense-cones. 



Ninth tergite is divided into three lobes, two lateral and one median. The 

 median lobe is irregularly dome-shaped with a chitinous plate nearly covering the 

 upper surface while the lateral lobe possesses a chitinous region from which arises two 

 setse mounted on tubercles. Two pairs of setae, arising from tubercles, are present 

 on the membranous area just lateral to the plate, the anterior pair being contiguous 

 with the plate. A ventral pair may be seen through the membrane, anterior and in 

 line with the other two. Acrocercus present on the under side of the lateral lobe and 

 terminates in two setse mounted on tubercles. 



Full-grown Larva. — Length, 5.8 mm.; width at the second to fourth ab- 

 dominal segments, 1.5 mm. The general color is grayish brown or dirty white. The 

 head, which is 0.3 mm. in length and a little less in width, is often retracted under the 

 pronotum as far as the ocular areas. First segment of antennae little less than the 

 second in length. Finger-like appendage of second segment about one-half the size 

 of the third, which has become more elongate. Mandibles much stronger. The 

 smallest inner tooth 3 of right mandible is smaller in comparison with the other teeth. 

 Maxillae more developed; stipes larger and considerably longer than palpus and pal- 

 pifer together. Legs not as long as thorax is wide. Viewed from the side, there seem 

 to be three lateral regions or tubercles on each abdominal segment; the dorsal and 

 ventral lateral regions of the intersegmental membrane are reduced so that only the 

 middle one is prominent. 



Pupa. — Length, 3.6 mm. (curled up); width at its thorax, 2.9 mm. Whitish. 

 Head smooth and bears two supraorbital styli on each side. Pronotum smooth, its 

 cephalic margin lobe-like in the middle. The styli are arranged in transverse rows as 

 follows: ten at the anterior margin, four in the middle at the posterior margin, the 

 two middle ones being shorter than the other eight and the most lateral one on each 



!A central colorless seta noted in some specimens and in L. minutus the anterior border of the 

 plate is emarginate. 



2 D'Orchymont, because a terminal papilliform tubercle bearing a seta is present, considers that 

 it may be two-segmented. The condition in Hydrophilus obtusatus tends to verify his opinion. 



ilndicates a tendency to disappear. Laccobius minutus has only two inner teeth on right mandible. 



