20 Bulletin American Museum of Natural History [Vol. XLII 



ventrally, the first ovo-oblong, the second somewhat rectangular, and the third tri- 

 partite with the middle bilobed, each lobe with a seta, the lateral parts triangular 

 and with a seta. 



Helophorus aquaticus Linnaeus 



The identical life history material of this European species used by 

 Schiodte in his work on this genus is located in the collection of the 

 United States National Museum but is in poor condition. An examina- 

 tion of the full-grown larva shows that the sclerites in front of the pro- 

 coxae are not so prominent as in the younger larvae. The abdomen is 

 only slightly more strongly chitinized than in the first stage larva and 

 the intersegmental membranes are present but not prominent. The 

 setae are lost in the specimen examined but this may be due to its poor 

 condition. The following pupal description may well be incorporated. 



Pupa. — Length, 8.5 mm.; width, 2.00 mm. at its thorax. Whitish (specimeu 

 browned with age). Head smooth and bears two supraorbital styli on each side. 

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

 with a large median lobe. Tue styli 1 are arranged as follows: ten on the lateral and 

 anterior margins, two of which are on the middle lobe; six on the posterior margin, 

 counting the two corner ones; no styli are to be seen in the central area of the pro- 

 notum but may have been destroyed. (Schiodte's figure gives none.) Mesonotum 

 and metanotum with a transverse row of two seta?. Inner spur of metatibia fairly 

 prominent.. All tarsi probably ending in a spme but not very clear and tibiae not 

 noticeably spinous on the outer side. Metathoracic pterothecse conspicuous from 

 above. First to seventh abdominal tergites with a transverse row of four styli. 

 Second to seventh pleurites each with a stylus, all arising from small conical tubercles; 

 eighth tergite somewhat semicircular, the rounded posterior border bearing two styli; 

 one lateral stylus noted on each side below the eighth tergite; ninth segment with a 

 pair of short, conical, fleshy cerci about the same length as the ninth tergite. They 

 diverge only slightly and their sharp tips point inwardly. 



2. Limnebiinae 



Eggs laid singly with a slight covermg of loosely applied silk. Larva with head 

 inclined ; antenna? with points of insertion situated nearer the externo-f rontal angles 

 than those of the mandibles; epicranial suture present; ocular areas round, convex 

 and in groups of five, not closely aggregated; labrum and clypeus both well developed; 

 mandibles each with a lacinia mobilis; maxilla primitive with an inner lobe; labium 

 with short palpi; flesh}' ligula present; labium and maxilla; inserted in a furrow on the 

 under side of the head; gula well developed and attaining the occipital opening. 

 Nine complete abdominal segments each with a ventral and dorsal plate, and a distinct 

 but reduced tenth or anal segment. Cerci two-segmented. Holopneustic type with 

 annuliform spiracles. 



ir The basal part of the stylus is short and the terminal seta long. 



