378 Journal of Agricultural Research voi. vi, no. 10 



were exposed to the parasite in vial cages and when ovipositing females 

 were placed in large glass chimneys containing growing wheat infested 

 with the Hessian fly. Occasionally the females have been observ^ed appar- 

 ently to oviposit in stems containing only larvge ; and although careful 

 dissections of these stems were made, no eggs were found. Further proof 

 that M. suhapterus normally oviposits in flaxseeds was obtained by dis- 

 secting puparia collected in fields where this parasite was numerous at 

 the time the collection was made. Both eggs and young lars'ae of a parasite 

 were present in the flaxseeds and when reared to maturity in the labora- 

 tory were found to be M. suhapterus. The t^gg stage in 1 19 cases varied 

 from I >^ to 5 days. Low temperatures in fall and spring retarded embry- 

 onic development. The larvse reared in glass cells emerged from the 

 eggshells by breaking through one end, and after crawling around a short 

 time settled down in one place to feed. 



THU L.'VRVA 



The full-grown larva of M. suhapterus (PI. II, fig. 6) averages 2 mm. 

 long by 0.75 mm. in thickness. It is white, with the pale-brown con- 

 tents of the alimentary tract showing through the body. There are two 

 pairs of slightly raised circular tubercles on the front of the head near 

 the top. The lower pair are slightly farther apart than the upper pair, 

 the former each bearing a small conical projection, evidently the an- 

 tennae, varying from white to brown and about 0.015 "^"i- long. The 

 median ventral surface of the head bears the round, suctorial mouth 

 opening. The only mouth appendages distinguishable are a pair of 

 very small brown chitinous mandibles borne laterally and closing to- 

 gether across the mouth (PI. LII, fig. 5). The distal ends of the man- 

 dibles are sharp and needlelike. The proximal ends are suddenly 

 enlarged, evidently to provide for muscle fastenings. A minute pit, 

 which sometimes appears to have a brown center, occurs on each side 

 of the mouth. The body is entirely glabrous, so far as could be deter- 

 mined, except for the anal segment, oval in shape, with the anal end 

 the more pointed. There are 13 segments besides the head, the anal 

 segment being divided into a dorsal and ventral lobe by a horizontal 

 fold across the end. The dorsal lobe bears four short, very fine setae in 

 a transverse row, these usually being in lateral pairs. The ventral anal 

 lobe bears only two very short, fine setae, one near each lateral end of 

 the lobe. 



The number of instars passed through by larvae of M. suhapterus in 

 making their growth appeared to be five. Five pairs of molted mandi- 

 bles increasing uniformly in size, from the small pair resembling those 

 borne by newly hatched larvae to the large pair molted off when full- 

 grown lar\^ae pupated, were present in almost eveiy mount made of 

 the material left behind in a cell where a larva had developed. In 



