NO. 1788. 



NORTH AMERICAN ERGA8ILIDJE— WILSON. 



311 



KEY TO SUBFAMILIES. 



a. Second antennse much elongated, forming stout clasping organs, ending in a single 



strong claw; maxillipeds entirely wanting in the female. . . .Ergasilin^, p. 311. 



a. Second antennse normal size, terminal joint roughened and ending in several claws; 



maxillipeds present in both sexes b. 



b. Maxillipeds turned forward outside, and partly in front, of the other mouth-parts; 



maxillary hooks not present Bomolochin^, p. 350. 



b. Maxillipeds in their normal position behind the other mouth-parts; maxillary 

 hooks present T.eniacanthin.e, p. 381. 



Subfamily ERG-^SILIlSr^. 



Body cyclindrical and elongate, the ventral surface of the carapace 

 projecting so that its edges can not be flattened clown upon any 

 surface to act as a prehensile disk. 



First antenna small, the basal joints neither enlarged nor flattened, 

 and moderately armed with slender set93. Second antenna elongated 

 into a powerful clasping organ, often half or even three-quarters as 

 long as the entire body, and ending in a single stout claw. Mouth 

 nearly in the center of the cephalothorax and projecting somewhat 

 from the ventral surface. First swimming legs like the other pairs; 

 fifth pair simple and one-jointed except in Thersitina. 



Species minute, from 0.6 to 1 millimeter in length. 



description op the mouth-parts. 



Female (fig. 27). — Mouth-parts removed some distance from the 

 second antennse. Labrum transversely elliptical or nearly orbicular, 



often so fused with the 

 head in the adult as to be 

 indistinguishable. Labi- 

 um flattened or even de- 

 pressed, and without hairs 

 or spines ; semicircular or 

 U-shaped, the convex side 

 pointing backward. In 

 the short space between 

 the labium and labrum are 

 found the mandibles and 

 first maxillae. The man- 

 dible consists of a stout 

 basal joint, armed with 

 a palp on its posterior margin, and a terminal joint, curved sharply for- 

 ward and heavily fringed with short setae around its entire margin. 

 The palp is also fringed with similar setse along its posterior margin 

 and at its tip. 



The two mandibles turn forward beneath the upper lip and overlap 

 each other across the mid-line. The maxillary hooks are lacking; the 



Fig. 27.— Mouth-parts of female Ergasilus centrarchi- 

 DARUM. lb, Labium; md, mandible; md. p., mandibular 

 palp; mi', first maxilla; mi", second maxilla. 



