NO. 1788. NORTH AMERICAN EROASILIDJE— WILSON. 345 



ERGASILUS MUGILIS Vogt. 

 Plate 47, text figure 9. 

 Ergasilus mugilis, Vogt, 1877, pp. 94 to 100. 



Female. — Cephalothorax two-thirds the entire length and nearly 

 twice as long as wide. First thorax segment distinctly separated 

 from the head by a deep groove which forms large lateral emargina- 

 tions. Head transversely elliptical, with a wide and evenly rounded 

 projection at the center of the anterior margin. First thorax segment 

 the same width and length as the head, but more quadrilateral in 

 outline, with rounded corners. Second, third, and fourth segments 

 diminishing regularly in* width, but about the same length, the 

 second one less than one-third the width of the first segment. Fifth 

 segment very short and thoroughly fused with the genital segment; 

 sixth or genital segment the same width as the fourth segment and 

 half as long again, barrel shaped, with rather flat sides. 



Abdomen three-jointed, the segments diminishing regularly in 

 width and length, the terminal one deeply incised posteriorly. Anal 

 laminae rectangular, about the same length as the last abdomen 

 segment, and each tipped with two rather short setae of unequal 

 length. Egg-cases half as long again as the entire body, somewhat 

 tapered posteriorly; eggs large, arranged in four or five longitudinal 

 rows, from 100 to 125 eggs in each case. 



First antennae six-jointed, the length of each less than one-quarter 

 of the width of the carapace, armed with very short setae, evenly 

 distributed among the joints. 



Second antennae slender, four-jointed, and reaching but little be- 

 yond the margin of the head; basal joint not inflated, second and 

 third joints tapering slightly, the former one-fourth longer than the 

 latter; terminal claw two-thirds the length of the third joint, strongly 

 curved and acutely pointed. 



Mouth-parts differing in several particulars from those of other 

 species; labrum very wide, its lateral edges reaching well beyond 

 the bases of the mandibles, its posterior margin nearly straight 

 (fig. 9). Mandibles entirely covered by the labrum, except the 

 posterior proximal corner of the basal joint; the diagonally opposite 

 corner (anterior distal) is armed with a good sized tuft of bristles; 

 the neck at the inner end of the basal joint is narrow; the cutting 

 blade is also narrow and four times as long as wide. 



The first maxillse are slightly overlapped by the labrum, and each 

 is armed with two nonplumose setae of about the same length. The 

 second maxillae have an elongate terminal joint, heavily armed with 

 bristles. Both mandibles and maxillae are attached so far apart 

 that they do not meet on the mid-line, but are separated by quite an 

 interval. 



