128 PROC. ENT. SOC. WASH., VOL. 23, NO. 6, JUNE, 1921 



parous, depositing upon the body of the host caterpillar thin- 

 shelled eggs containing larvae ready to hatch immediately. The 

 larva resembles in general structure the maggots of ordinary 

 Muscids, such as the House-fly. Like the latter, it passes 

 through three morphologically distinct stages separated by 

 moults. The pupal stage is passed within the hardened skin 

 of the last stage larva which forms the characteristic pupanum. 



TECHNICAL DESCRIPTION. 



The egg measures about 0.65 mm. x 0.175 mm. It is approximately cylindri- 

 cal, tapering slightly anteriorly; the chorion is colorless and presents under 

 high magnifications a fine punctuation. 



The first stage larva measures about 0.65 mm. x 0.175 mm. It is moderately 

 elongate (Fig. 1), cylindrical, tapering rather abruptly posteriorly, more gradu- 

 ally toward the anterior extremity; the cuticle is colorless and transparent; 

 the body is composed of 11 segments and a minute head or pseudocephalon; 

 the cuticle is colorless, transparent and unsculptured, bearing bands of minute 

 dark spines. These bands of spines are broadest on the thoracic segments and 

 particularly on segment II. On the abdominal segments they are narrower and 

 here the dorsal part of each band is separated from the ventral part by a small 

 pleural space in the middle of which there exists a small, isolated patch of spines. 

 On segments I-VI inclusive, the bands of spines are situated on the anterior 

 region of each segment, but on segment VII there appears, just in front of the 

 dorsal extremity of the ventral spine-band of segment VIII, a small isolated 

 group of spines situated near the posterior border of the segment. On segment 

 VIII, below a similar patch, there sometimes appears a short ventral row and a 

 similar dorsal one, running parallel to the band on the anterior border of the 

 segment following and on segment IX there is a complete posterior band of 

 spines, broadest in the pleural region. On the posterior border of segment X a 

 similar band exists. As one passes toward the posterior extremity of the larva, 

 the bands of spines on the anterior border of the segments become narrower and 

 less important so that on segment X the pleura! group has disappeared, while on 

 segment XI only a few pleuro-ventral spines remain on the anterior border. 

 The spines on the anterior border of the segments of the larva are directed for- 

 ward while those on the posterior border are directed backward. The dispo- 

 sition of the spines on the last segment is rather unusual and serves to distinguish 

 this species at once from the other Tachinid parasites of Pyrausta so far studied. 

 On this segment there exists, in addition to the few ventro-lateral spines already 

 mentioned, a ventral band traversing the middle of the segment, 

 interrupted a short distance on either side of the median line, so as to isolate a 

 median group, and, finally, between this band and the posterior extremity, a 

 ventral patch of spines for the most part much heavier and darker than the 

 other spines of the body and directed forward. Opposite the ventral group, on 

 the dorsal surface, is a similar group (Fig. 2), which is slightly larger and situated 

 between the pleural extremities of the median ventral band. These two groups 

 of spines bear a functional relation to the posterior stigmata similar to that of 



