136 THE ENTOMOLOGIST. 



In this genus, unlike the majority of tiie Braconidce, the 

 whole of the metamorphoses of the parasite take place within 

 the body of the host. At the time the parasite larva is full 

 grown a sticky liquid, which soon solidifies, exudes from the 

 unfortunate caterpillar and so fixes it firmly to the leaf or twig 

 on which it may be resting ; this same liquid is the cause of 

 the hardening of the skin of the host which takes place at 

 about the same time, but only after the entire contents have 

 been devoured. Some species weave a distinct but flimsy 

 cocoon within the indurated skin, but others seem to merely 

 strengthen the walls of their prisons by the addition of a few 

 threads. There can be no doubt that the blown-out appearance 

 of the skin is deliberately caused by the movements of the 

 parasite larva while the skin is still in a flexible condition. 

 Having attained the imago state the parasite bores a hole in 

 the posterior dorsal segments of the host-cocoon and so escapes. 

 The period passed within the cocoon varies from three weeks 

 to nine months or even longer, according to the season and 

 species. 



In 'Trans. Entom. Soc.,' 1885, p. 88, the Rev. T. A. Marshall 

 published a table of twelve British species, relying in a great 

 measure on coloration for his distinctions. Little or nothing 

 more was done in this country until in 1916 Morley tabulated 

 the palsearctic species ('Entom.,' xlix, p. 85), basing his work on 

 the characters brought forward by Thomson (' Opus Ent.,' xvi). 

 This useful table is of great assistance in determining the 

 British species, though the instability of the colouring and 

 nearness of relationship create difiiculties in some cases, and 

 I am inclined to think that with the first nineteen species 

 tabulated the length of the hind calcaria when compared with 

 the tibige has been exaggerated. 



I am confident that until the breeding of these interesting 

 insects is taken in hand more thoroughly we shall never be 

 quite sure of the extent and variation of our native species, for 

 it appears to me to be more than likely that the nature of the 

 host ma.y to a certain extent determine the colour, if nothing 

 more, of the parasite. It is also quite possible that at present 

 we have nearly related but quite distinct species confused under 

 one name. 



Twenty species have now been recorded as British. 



(To be continued.) 



