392 



The Large Larch Sawfly. [oct, 



observed a female in confinement, and thus describes the egg- 

 laying : — " The sawfly stood head downward while engaged in 

 making the puncture, and was not disturbed by our removing 

 the larch twig from the glass jar and holding it in our hand 

 while watching the movement of the ovipositor." (This same 

 restfulness I have observed in the pine sawfly [L.pini) while 

 watching a female in captivity laying her eggs.) " The serrated 

 blades of the ovipositor were thrust obliquely into the shoot by 

 a sawing movement. After the incision was sufficiently deep 

 the egg was forced out of the oviduct by an evident expulsive 

 movement of the muscles at the base of the ovipositor. The 

 slit or opening of the incision after the egg has passed into it is 

 quite narrow and about if mm. in length. While engaged in 

 the process the antennae are motionless, but immediately after 

 the ovipositor is withdrawn they begin to vibrate actively, the 

 insect being then in search of a site for a fresh incision." As 

 the embryo develops the slits in the shoots gape a little, and 

 through the oval hole the caterpillar creeps on hatching. The 

 caterpillars may begin by gnawing the single leaves on the 

 young shoot, but they soon pass to the clusters of needles on 

 'the dwarf shoots. Single leaves may be eaten so that the edges 

 appear serrated, or the clusters of leaves may be half eaten 

 or quite destroyed so that only stumps are left. 



In the young condition the caterpillars may be found in 

 clusters. The caterpillars assume various positions, arranged 

 with the tail end curled round the shoot ; or like a mark of 

 interrogation, or the letter S ; or (a characteristic attitude) with 

 the hind half of the body turned upwards and over the front 

 half. On being handled the caterpillars would wriggle violently 

 rolling themselves about in a fashion that reminded one of sur- 

 face caterpillars, and ultimately lying on their side with their 

 body forming a circle, the tail end touching the head. 



The larv^ are to be found at work during the summer, and 

 most numerously in July and the first fortnight of August. By 

 the end of August most have left the trees. Some, however, 

 do not complete their growth till September. I kept some in 

 confinement that made their cocoons in the second week of 

 September. The full fed caterpillars leave the trees and pass 

 into the moss or litter or the soil below, and in such shelter 

 places spin the cocoon in which they pass the winter. They lie 



