i9o6.] The Large Larch Sawfly.. 393 



somewhat bent in the cocoon until the late spring or summer of 

 the next year, when they turn to pupae, the adults issuing in 

 due course. 



There is no evidence so far that there are two generations in 

 the year, and yet the caterpillars seem to attain full size in 

 a comparatively short time. It is interesting and sometimes 

 puzzling as to why from cocoons collected and possibly 

 made at the same time and kept in the same conditions, 

 there should be such variations in the escape of the adults, 

 For example, in my recent experiments with Lophynis pint, 

 the Pine Sawfly, in 1905, from cocoons collected in the winter 

 of 1904 and kept indoors, 117 adults issued, these insects 

 appearing on thirty-seven different days between April and 

 August, the first coming away on April 14th, and the last on 

 AxUgust 1st. In 1906, from a number of cocoons made by 

 the caterpillars in confinement in 1905 and kept indoors 

 104 adults issued, the insects appearing on thirty- two separate 

 days, the earliest on the first of June and the last at the end 

 of the first week of August. The practical import of this 

 is that as egg-laying takes place at different times according 

 to the different flight times of the adults, infestation must 

 be expected not merely at some limited definite period, but any 

 time during the summer when the temperature is favourable. 



Tree Attaeked. — Infestation in the larches in Cumber- 

 land was upon trees of from twenty to seventy years of age. The 

 records elsewhere show that young plants of ten years of age 

 may be attacked, but attack has been reported more frequently 

 on older and taller trees. In one case in Washington County, 

 United States, larches less than 25 ft. high had been spared, but 

 of those of 30 ft. and upwards 90 per cent, had been attacked 

 and almost completely defoliated. The fact that the caterpillars 

 work on well- grown trees, and it seems characteristically at the 

 crown first, increases greatly the difficulty of fighting them. 



Preventive and Remedial Measures. — i. As against the adults 

 scarcely anything can be done effectively. They lay high up, well 

 out of reach, so that the placing here and there of tarred boards 

 standing erect and with the tar frequently replenished, which is 

 practised sometimes against sawflies that lay on young plants, 

 cannot be tried with hope of success. 



2. If young trees chance to be affected with the caterpillars, 



