BULLETi:sr 1088, XJ. S. DEPARTMENT OF AGRICULTURE. 





Fig. 3. — Brown - tail moth 

 caterpillars containing pu- 

 paria of Zygobothria ni- 

 dicola. 



THIRD-STAGE MAGGOT OF THE PARASITE. 



When the second-stage skin is molted it is pushed back upon the 

 funnel, as was that of the first stage; the mouth hooks of the two 

 instars at this time are easih^ seen on the mass of yellowish tissue that 

 surrounds the chitinous funnel itself. The 

 particular points of difference between the 

 second and third stage maggots are the larger 

 size of the latter and its much heavier mouth 

 hook. The mouth hook is divided longitudi- 

 jftt/k nally as in the second stage, but there are now 



'^''' two joints in the anterior part of the skele- 



|^|MJ|itt^ ton, one near the middle, corresponding to the 



^^^^^^ single joint of the second stage, and another 



near the base of the very broad posterior 

 plates. The anterior spiracles, opening be- 

 tween the second and third body segments, 

 are much more distinct than in the second 

 instar. 



This stage is the shortest of the three, requiring only four or five 

 days. The host larva is killed just before the end of this period, 

 with the destruction 

 of its vital organs, 

 and the parasite 

 forms its puparium 

 in the integumental 

 funnel inside the 

 host. 



The pupariimi is 

 about 8 mm. long 

 and is dark brown- 

 ish red in color; the 

 posterior end is a 

 little depressed, and 

 the two anal stig- 

 mata (Fig. 4) with- 

 in the depression are 

 slightly elevated. 

 Dead caterpillars 

 that contain puparia 

 of Z. nidicoJa (Fig. 

 3) are easily detect- 

 ed; they are greatly 

 shortened, being scarcely longer than the puparia within, and are 

 slightl}^ inflated. 



The period spent in the puparium averages from 25 to 30 days,, 

 after which the flies appear, some 8 to 16 days prior to the hatching 



Fig. 4. — Anal stigmata of puparium of Zygobothria nidicola. 



