Tenthredinidae 487 



inserting pins through both wire and cloth. One female was placed 

 in each cage. In some instances males were confined with the females 

 for certain experiments, but this is unnecessary because the species is 

 parthenogenetic. In the cages the females oviposit freely and the eggs 

 develop normally. 



In using these cages two important points should be remembered: 

 first, that the females in ovipositing always rest with the head toward 

 the end of the shoot and therefore require that the new growth be at 

 least y. 2 inch in length and preferably longer; and, second, that in placing 

 the cage on the branch allowance must be made for the growth of the 

 shoot. 



Larvae. The larvae of the larch sawfly are gregarious and move 

 about very little. Therefore they are very easily handled. They must, 

 however, be provided with a continuous supply of fresh food. This is 

 very important because even a short period of starvation of the larvae 

 may result in the sterility of the adult females. For this reason it was 

 usually most convenient to rear them on living trees, although they were 

 also successfully reared in cages where they were fed on cut branches 

 set in water to keep them fresh. When they were fed on cut branches it 

 was necessary to change the branches every day or two. 



When rearing was conducted on the living tree the oviposition cages 

 were removed before the eggs hatched. Adjacent branches were cut 

 away so that none were in direct contact with the branch on which the 

 rearing was conducted. In order to prevent the larvae from making 

 their way to other branches a tanglefoot band was placed around the 

 branch. Beneath the rearing branch a tray with muslin bottom and 

 tanglefoot around the edges was fastened, usually on a post set in the 

 ground and sufficiently high to bring the tray within a foot of the 

 branch. The rearing branch was then fastened to the tray by wires so 

 as to prevent the wind from moving it away from the tray. Thus any 

 larvae that dropped from the branch were caught and confined in the 

 tray until they could be cared for. 



Ordinarily the larvae remained on the tree until they were fully fed 

 and ready to make cocoons. They were then removed and placed in 

 woven wire cages. Fresh food was provided in these cages for larvae 

 that might have fallen into the tray by accident before they completed 

 feeding. 



Cocoons. The cages mentioned above were cylinders of wire cloth 

 about ten inches in diameter and a foot high with a wire bottom and 

 removable cloth top. Three inches of moist sphagnum moss was placed 

 in the bottom. After the larvae had made their way into the moss and 

 spun their cocoons the cloth tops were replaced with wire and the 

 cages were placed in a nearby swamp where they were sunk in the moss 



