OVIPOSITION AND INCUBATION OF PANISCUS (PAR.) VIRGATUS. 211 



possess the greater share of this, the ichneumon will not again 

 interfere for a long time ; not at all, I suspect, in a state of 

 nature, as they would go their separate ways. 



That this seizing of the enemy by the leg is a strongly 

 instinctive action I should think probable, from having seen a 

 larva of Hybernia defoliaria do it every time a species of 

 Anomalon I kept in the same box with it approached, though 

 without any sinister intent on the parasite's part. 



The ovum itself of P. virgatus is long, black, and shining, 

 somewhat rounded at one end, and very pointed at the other, and 

 is attached to the host at this pointed end by a fine foot-stalk. 

 In this light red, semi-transparent parasite, the ova can be seen 

 lying as a dark mass towards the apex of the abdomen ; on dis- 

 secting a captured female I counted thirty-seven, but this may 

 not represent the full batch, as it is likely some might have 

 already been deposited. Those nearest to the apex and ready 

 for ejection were quite dark, but higher up they were whitish, 

 beginning to turn black at the blunt end, and higher still they 

 were quite light. 



Oviposition takes place upon boreata larvae usually from one 

 to two days before they are about to commence pupation, the 

 ova hatching when they have spun their cocoon ; until this time 

 the egg has remained in a more or less perpendicular position, 

 but the young grub, partly emerging from the rounded end, 

 causes a top-heaviness, which bends over the foot-stalk, allowing 

 the parasite's mouth to come in contact with its food. It does 

 not emerge entirely from the egg-shell for some time, but 

 continues to feed, growing rapidly, until the shell is merely 

 attached to the apical segment. By this time death has over- 

 taken the caterpillar, and the parasite, which has hitherto been 

 lying round its neck, now alters its position, withdraws its last 

 segment from the shell, and lies alongside its victim in the 

 cocoon, continuing to feed on its body. 



The length of incubation varies according to the state of 

 advancement of the host towards pupation, the time of hatching 

 being when the Cheimatobia has spun its cocoon, and before it 

 has assumed the pupal state. Normally, as before mentioned, 

 the ova are deposited shortly preceding the host's retirement to 

 its cocoon ; should they almost immediately do this, I found the 

 ova would hatch on the morning of the third day after 

 parasitization. 



That the desire of the host for pupation does influence the 

 parasite within the egg, and that it can and does await the 

 psychological moment when to emerge is evident, as by substi- 

 tuting Hybernia defoliaria larvse, not nearly full-fed, for those of 

 Cheimatobia boreata, and thus compelling Paniscus virgatus, who 

 were anxious to be rid of their ova, to reluctantly oviposit 

 upon them, I found that the length of incubation could be 



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