SEPTEMBER, 1865. 267 



discovery, that puts an end to all uncertainty respecting the 

 larva and its food plant. 



In a subsequent letter Mr. Walsh kindly supplied me with 

 the following description of the larva : 



" Length *20 inch. Body tapering at each end, opaque, 

 milky-whitish, with a few short, whitish hairs. The first 

 segment behind the head, with an obsemicircular, shining, 

 glabrous, brown, dorsal shield ; second segment with an inter- 

 rupted, opaque brown, dorsal band on its anterior edge, the 

 interruption occupying about one-third of the band; segments 

 3 — 12 with an uninterrupted, opaque brown, dorsal band on 

 the anterior edge, and segment eleventh with a similar band 

 at its tip also. Head yellowish. Legs and venter immacu- 

 late, whitish. Legs six, prolegs ten, normally arranged. 

 Spins a thread, wriggles much when disturbed and runs back- 

 wards with great agility. 



" This larva occurred in abundance August 23rd, and sub- 

 sequently in the Tenthredinidous gall, S. pomum, Walsh, MS., 

 which grows on the leaves of Salix cordata. Each gall 

 contained but a single larva, unaccompanied by the larva 

 of the Nematus which makes the gall, which it must con- 

 sequently have destroyed or starved out, either in the egg or 

 in the larva state. 



" A single imago came out in the autumn of the same year, 

 but the great bulk of them came out next spring, May 8th — 

 20th, from galls kept through the winter. There can be no 

 doubt of the correlation of larva and imago, because no other 

 Lepidopterous larva or imago occurred in the gall S. pomum, 

 though I had three or four hundred of them in my breeding- 

 vase. The insect must hybernate normally in the larva state, 

 for I noticed numbers of them in the spring crawling about 

 among the galls. In a state of confinement it generally retires 

 to the inside of the gall to assume the pupa state, though I 

 noticed one or two cocoons spun among the galls. Probably 

 in a state of nature it hybernates in the gall, comes out of 

 it in the spring, and spins its cocoon amongst dry leaves and 

 rubbish. 



