AN ATTACK BY SAWFLY LARV^. 53 



cular case spraying was most effective, still one could readily 

 understand that heavy showers of rain following the spraying 

 operation would be apt to wash the Paris green off. 



In spite of our efforts a large number of the larvae passed into 

 the cocoon stage about the 20th of July. Some which I kept in 

 captivity emerged from the cocoons towards the end of August, 

 when I noticed for the first time that the saw-fly was not the 

 common form Lophyrus pint, and I suspected Z. rufus. This 

 suspicion was confirmed on my sending specimens for identifi- 

 cation to Dr MacDougall, who informed me that the species 

 was believed to have only one generation in the year, and that 

 the eggs laid by the flies which emerged in early autumn pass 

 the winter as eggs. This has proved to be the case. Hatching 

 began on the 15th of May 1907, and continued till the beginning 

 of June. On the first signs of hatching I sent two men with 

 hedge gloves to crush the young broods. This was fairly easily 

 done, as at this stage the insects do not exceed an eighth part of 

 an inch in length, and are in compact broods on individual 

 needles of the plants instead of being scattered over the shoot as 

 is the case when they grow larger and more voracious. 



The plantation has been gone over four times this year, and 

 while I should not care to maintain that every larva has been 

 killed, still, I think few have escaped. Last year ^^2, 14s. pd. 

 was spent in combating the attack. This year the figure has run 

 up to £^(). The damage was severe last year, but is compara- 

 tively trifling this year, not because there were fewer insects but 

 because they were dealt with as they hatched out and never 

 reached their most voracious stage. 



It is to be noticed that L. rufus is at all stages rather smaller 

 than Z. pini. When first hatched out the larvae of the former 

 are about one-eighth inch long, with glossy black heads and dull 

 grey-black bodies. When full-fed they are about three 

 quarters of an inch long, with glossy jet black heads and dull 

 grey-green bodies. There is a lighter longitudinal stripe down the 

 back, and a broken black line above the abdominal and thoracic 

 feet and legs. The body narrows from the thorax to the rear 

 extremity, which is grey-black in colour. The thoracic feet have 

 light and black bands alternately. There are 16 prolegs and 6 

 thoracic legs. In common with other sawfly larvae, Z. rufus 

 when disturbed takes the characteristic S shape. 



