44 RESULTS FROM GIPSY MOTH PARASITE LABORATORY. 



Perilampus Tiyalinus in this case always remains endoparasitic 

 throughout the winter, at least so far as our observations go, and 

 several hundred cocoons have been examined to date. At first it 

 seemed rather puzzling that the same species should pass the winter 

 ectoparasitically upon tachinids and endoparasitically upon, Limne- 

 rium validum, but dissections of hundreds of the puparia and cocoons 

 brought to light the fact that the habit of Perilampus in this regard 

 was dependent entirely upon the life cycle of the host parasite, that 

 is to say, the planidium lives internally in its host until histolysis 

 takes place, when it changes its mode of life from an internal parasite 

 to an external parasite. Varichxta pupates in the fall, so the pla- 

 nidium makes its exit at this season of the year and hibernates 

 externally. Limnerium validum hibernates as a larva and pupates 

 in the spring, hence the planidium in this case remains internal until 

 spring, when it emerges by means of its efficient mandibles and spined 

 head, completing its development in precisely the same manner as those 

 individuals which happen to have chosen Variclixta as their host. 

 The internal disturbances which take place in the body of the host 

 at the time of histolysis probably act as a stimulus to the activities 

 of the planidium, and the condition of the integument is such as to 

 make the exit of the secondary parasite especially easy at this time. 

 The development of the host, so far as our observations have gone, 

 invariably ceases at the time of the exit of the planidium. Whether 

 or not it is actually killed at this time is not evident. In any case 

 decomposition does not take place immediately, the host being left 

 in a condition somewhat comparable to that of the prey of certain 

 aculeate Hymenoptera. 



As A Parasite of Summer-Issuing Hymenoptera. 



The other primary parasites of Hyphantria from which we have 

 reared Perilampus are two additional species of Limnerium, differing 

 from L. validum in that they spin their cocoon within the skin of the 

 caterpillar and emerge in the fall, and the braconids Apanteles hypJian- 

 trise Riley and a Meteorus (probably M. communis Cresson). In all 

 four of these species the Perilampus completes its development at 

 once. Whether or not these individual specimens manage to survive 

 the winter is open to question. It is quite possible that many of 

 them remain within the cocoon of their host throughout the winter. 

 This is quite strongly indicated by the result of an experiment in 

 which a collection of old webs containing cocoons of the several 

 parasites was made on October 20, 1908, from which several adult 

 Perilampus issued between 6 and 10 days later. The material 

 was kept in a warm room; had it remained out of doors it is very 

 unlikely that emergence would have occurred so soon, and probable 

 that it would have been deferred until spring. 



