LIFE-HISTORIES AND BIONOMICS OF SOME TACHINIDiE. 115 



were taken out of the stove and kept under normal conditions, 

 and none have shown any signs of emergence up to the present 

 date (April 6th). This persistence to remain over a lengthened 

 period in the pupal stage — in spite of such great heat — seems 

 rather curious, particularly as the Tachinidse belong to a group 

 of insects whose development is often completed in a few weeks, 

 and frequently much influenced by temperature. 



The TachinidsB have, I think, a certain number (perhaps two, 

 three, or four) of broods* in the year, and cannot be induced to 

 give rise to an additional one by artificial means. This at any 

 rate appears to be the case in the autumn, but if extra heat be 

 applied throughout the summer months some effect would pro- 

 bably be witnessed. No doubt the Tachinids obtained from the 

 S. lubricipeda larvae had lived during the earlier part of the 

 season in another species of lepidopterous larva, and those 

 individuals bred in September represented the second or third 

 brood. 



I have also obtained several species of Tachinidse from En- 

 dromis versicolor, Linn., Saturnia carpini, W. V., and S. pyri, 

 W. V.t; in these instances one caterpillar supported three or 

 four parasites instead of one only, as in A. grossulariata and 

 S. lubricipeda. The winter was passed in the pupal stage, and 

 my observations contribute to the belief that most, if not all, of 

 the Tachinidae probably remain in this state throughout the 

 winter. 



In most cases the emergence of the Tachinids from winter 

 pupae takes place about the same time as the emergence of the 

 hosts, i. e. those obtained from E. versicolor emerged in April ; 

 the species parasitic on S. carpini in late May and June ; those 

 from S. pyri in July; and I expect the pupae bred from S. lubri- 

 cipeda will produce the flies in June. It seems impossible, 

 therefore, that one species of Tachinid can ever be confined to 

 one host or even to hosts belonging to one genus. 



About the beginning of June, 1907, I received a few speci- 

 mens of a Tachinid from Mr. L. W. Newman which had been ob- 

 tained from the larvae of Sesia tipuliformis, Linn. This species, 

 Pelatachina tibialis, Fin., is of economic importance, the "cur- 

 rant clearwing," which it parasitises, being one of the commonest 

 of the Sesiidae, and often very destructive to our currant-bushes. 

 How the S. tipuliformis larva becomes parasitised I do not know, 

 as it lives in the pith of the stems of currant-bushes, and it is 

 difficult to conceive how the fly is able to deposit its ova in a 

 suitable position for the resulting larvae to infect their host. 

 Mr. Wainwright informs me that Pelatachina tibialis, Fin., has 



* This number of broods will vary according to the species, but most 

 probably two or three will be the usual number. 



f Masicera silvatica, Fin., a species which is parasitic on S. pyri, and 

 other hosts; it is a Continental species, and very little known as British. 



K 2 



