THE ENTOMOLOGIST. 125 



changes ; but this objection does not apply to the gall-insects 

 and Ichnevinions : in these the envelope is so very trans- 

 parent that, from the time they leave the larva state until they 

 become imagos, every alteration may be noted by simply 

 removing the pupas from their galls or cocoons, and placing 

 them in glass tubes, which should be stopped with cotton 

 wool and kept in the dark. In this vvay I have been much 

 interested, during the past spring, in watching the gradual 

 development of many of the above-named insects ; and I 

 must say that many of my former opinions have undergone a 

 great change. For instance, I found that at no time did they 

 appear to be without life or motion, but at intervals small pel- 

 lets of softfrass were ejected, shoeing that even digestion was 

 in some vvay in active operation ; also that the beautiful red, 

 yellow, and black colours of the imago were developed from 

 the internal fluids by natural causes, and not from the action of 

 light at all, light only having been admitted while they were 

 under examination. But perhaps a short life-history of the 

 Ichneumon which infests the larva of Zyga^na Filipendulae 

 will better illustrate the subject. In April this parasite lays 

 a solitary egg on the back of the larva of the Zygtena. This, 

 having come to life in a few days, eats its way through the 

 skin, and commences feeding upon the fatty portion of the 

 caterpillar. By the end of June the lepidopterous larva is 

 full-fed, and spins a white, sickly-looking cocoon ; but in- 

 stead of changing into a pupa it produces a stout hyme- 

 nopterous maggot, the larva of the future Ichneumon. Having 

 devoured the whole of its supporter, with the exception of the 

 skin, it spins for itself a hard cylindrical cocoon at the end of 

 that previously spun by the Zygaena larva, and, if not dis- 

 turbed, would remain in this until the following March or 

 April. It is now about eight lines long, pale yellow, onisci- 

 form, and very lively. No perceptible change takes place 

 until the end of January, when the eyes become darker, the 

 body more attenuated, and numerous pellets of frass are 

 ejected. By the end of February the waist is clearly defined, 

 and the antenna^, legs and wings show through the shell ; 

 by the second week in March the whole of the members 

 stand clear of the body, each encased in a transparent 

 covering ; after this the change goes on more rapidly ; minute 

 atoms of a dark colour, commencing at the head, gradually 



