512 



A. lacteicolor within them also become active and develop very rapidly 

 at the expense of the host, which generally dies wdthin 7-12 days after 

 the commencement of feeding, and shortly after this the full-grown 

 parasitic larva issues. The cocoon of A. lacteicolor is immediately 

 begun, and is completed in about 3 hours. The cocoons of the 

 wintering generation usually occur in the webs of brown-tail moth 

 caterpillars, while those of the summer generation occur on the 

 underside of leaves, in crevices of the bark, etc. The adult emerges 

 from the pupa after 5 to 8 days, mating and oviposition probably 

 occurrmg Avithin 48 hours. Fertihsation is not necessary for repro- 

 duction, but unfertilised females produce only males. With regard 

 to the summer host of A. lacteicolor, tne gipsy moth [Lymantria dispar] 

 is the only host at present known which is acceptable to the parasite 

 and is available at the time of appearance of the adult parasites of 

 the first generation. The life-cycle of the summer generation of 

 A. lacteicolor occupies 19-20 days and adults issue from gipsy moth 

 larvae during late June and early July. Between this date and the 

 time of oviposition in the hibernating caterpillars of N. phaeorrhoea 

 there is a period of more than a month, leaving ample time for another 

 generation. Observations in both field and laboratory indicate 

 Apatela hasta as the most probable host for A. lacteicolor during this 

 period. 



The importance of A. lacteicolor is due to several factors. It 

 parasitises as many as 20 to 25 per cent, of the larvae of N. phaeorrhoea, 

 and has several generations annually, also parasitising to a certain 

 extent the gipsy moth and certain native injurious species, including 

 Datana ministra and Hyphantria cunea. As its hosts are destroyed 

 in their early stages, they are not able to do a large amount of damage 

 before their destruction. On the other hand, the dependence of the 

 parasite for over- wintering upon the brown-tail moth, which is now 

 in a state of decadence, will largely reduce its usefulness as a parasite 

 of the gipsy moth and other species. The cocoons of the first generation 

 of A. lacteicolor are well protected from secondary parasites within 

 the webs of the brown-tail moth, but among the later generations 

 the hyperparasites found include Monodontomerus aereus, Wlk., 

 Pteromalus egregius, Foist., Dihrachys houcheanus, Ratz., Dimmockia 

 sp. , Habrocytus sp. , Pezomachus sp. , and two species of Hemiteles. 



Meteorus versicolor, which is re-described in this paper, oviposits 

 in young larvae of the brown-tail moth during August and early 

 September, and 5 or 6 days later the larva issues from the egg and 

 moves freely in the body cavity of its host. The larva feeds and 

 develops very little during the autumn and passes the winter in the 

 body cavity of its host, Nygmia phaeorrhoea being the only species 

 as yet knowTi to serve as a winter host. In the spring when the brown- 

 tail moth larvae resume feeding, the larvae of M. versicolor again 

 become active and after 10 to 14 days the cocoons of the parasite 

 appear. The host larva generally reaches the second instar and is 

 not killed before the emergence of the parasite, but dies about 24 hours 

 later. The cocoons of M. versicolor are generally spun at a little 

 distance from" the host and are suspended from a twig or branch. 

 The pupal period lasts 4 to 6 days, the adult emerging during the 

 first 2 or 3 weeks of June and leaving the pupal case suspended. The 

 adult life of M. versicolor is very similar to that of A. lacteicolor. 



