114 THE ENTOMOLOGIST. 



It appears that not more than one Tachinid larva is ever 

 present in one caterpillar of A. grossulariata, although I have 

 found two or three individuals of another species of Tachinid 

 parasitic on one larva of Saturnia carpini, W. V., Endromis 

 versicolor, &c. 



The pupal stage lasts approximately a fortnight, the flies 

 beginning to emerge about the end of June, and continuing for a 

 week or more. The flies differ greatly in size, some being half 

 as large again as others ; a fact which is no doubt accounted for 

 by the quantity of nourishment acquired during the larval 

 period. The flies live for about a week or ten days in confine- 

 ment, but seem to take no heed of any lepidopterous larvae when 

 l^laced in a cage with them. How these flies exist between this 

 date, June, to the beginning of May in the following year is not 

 definitely known, but Mr. Hewitt suggests that the Tachinid has 

 another brood, and that this brood lives in another species of 

 lepidopterous larva. This view is strengthened by the fact that 

 many records exist of one species of Tachinid infecting different 

 species of lepidopterous larvae,. and it is even suggested that one 

 species of Tachinid might parasitise not only insects belonging to 

 a different species or genus, but of a different order. 



A. grossulariata has only one brood* in the year, and if 

 Blepharidea vulgaris is confined to it, the flies must survive much 

 longer in the perfect state than they do in confinement. 



The young larvae of A.grossidariata do not appear until about 

 the first or second week in August, which would mean the flies 

 living for six weeks at least before being able to deposit any ova. 

 Even then the A. grossulariata larvae are extremely small, and I 

 think it very improbable these Tachinids would infect them. I 

 think that B. vulgaris selects a species of lepidopterous larva 

 which is about half grown in early July on which to deposit its 

 eggs. In this case the resulting larvae would probably be full- 

 grown about the same time as the host, and pupation take place 

 some time in August. These pupae would then remain unhatched 

 until the following April, when there would be A. grossulariata 

 larvae available for infection. 



During September, 1 907, I collected about one hundred larvae 

 of Spilosoma luhricipeda, Linn., from which I bred twelve 

 Tachinid larvae. These appear, from the pupae, to be a much 

 larger species than Blepharidea vidgaris. About the second week 

 in September the Tachinids pupated, and this agreed exactly 

 with the time of pupation of S. lubricipeda. I attempted to force 

 these pupae by placing them on October 18th in a stove, the 

 temperature of which varied from 70° to 85° F. The result was 

 that they absolutely refused to be influenced by the abnormal 

 heat, which was allowed to act for six weeks. Afterwards they 



■= A partial second generation occasionally arises. 



