5 56 HYMENOPTERA 



skin remains entire, and is shuffled down to the extremity of the 

 body, but cannot be completely detached owing to the anchoring 

 of the posterior part of the body to the caterpillar ; the cast 

 skins thus remain as envelopes to the posterior part of the body. 

 jSTewport states that if the mouth of the parasite be detached, it 

 usually cannot again seize hold of the victim, and consequently 

 perishes. It is a curious fact that more eggs than one caterpillar 

 can support are habitually placed on it, and some of the resulting 

 larvae of necessity perish during the period of growth. Poulton, 

 who has recently made some additional observations on the 

 development of Paniscus} says that if three larvae are close 

 together, it is the middle one that perishes, and suggests 

 that this is due to some simple physical condition. From 

 Newport's account it may be gathered that the Mamestra 

 retains sufficient vitality to form its cocoon, and that the 

 Paniscus larvae likewise construct their own cocoons within 

 that of the Maviestra. In the case of Panisms cephaloies 

 feeding on Bicranura vinula, Poulton relates that the latter died 

 after the twelfth day of attack. The parasites, having relaxed 

 their hold on the victim just previous to this event, then thrust 

 their heads into the dead body, and devoured the larva, leaving 

 only a dried and empty integument. These larvae span a loose 

 sort of web in which to undergo their metamorphosis. In a 

 natural state, however, they form cocoons inside the cocoon of 

 the Bicranura. The period passed in the pupal condition was 

 about four weeks. This parasite only attacks the Lepidopterous 

 larva during the last stage of its existence as a larva, but the 

 eggs may be laid on the victim in an earlier stage ; and in such 

 case De Geer has stated, and Poulton has confirmed the observa- 

 tion, that though the larva sheds its skin it does not get rid of 

 the eggs. 



The little Ichneumons of the genus Pezomachus are quite 

 destitute of wings and somewhat resemble ants ; they are 

 common Insects in Britain. Only the female sex is known, and 

 it is believed that the winged Ichneumons assigned to the genus 

 Hemitdes — of which no females are known — are the males of 

 Pezomachus. Eepeated efforts have been made to place this 

 beyond doubt, but they have usually failed, for when a brood of 

 these parasites is reared, the individuals generally prove to be 



^ Tr. cnt. Hoc. London, 1886, p. 162, and 1887, p. 303. 



