112 FORESTRY IN NEW ENGLAND 



8o's, great destruction of the native larch was caused in New- 

 England. The insect will also attack the European larch. 



The following account of the appearance and life history of 

 the insect is quoted from an article by Dr. C. Gordon Hewitt, 

 F.E.S., Dominion Entomologist of Ottawa, Canada, and pub- 

 lished in the Report of the Canadian Forestry Convention for 

 1911: 



"The habits and Hfe history of the insect are such as to 

 render it injurious in both the caterpillar or worm stage, and the 

 fly stage. The winter is passed by the larva in a cocoon under the 

 turf round the base of the tree. In May the larvae transform 

 into the perfect insect and the flies begin to emerge during that 

 month. An interesting feature of the productive powers of the 

 larch sawfiy is that it can reproduce parthenogenetically, this 

 means that the females can deposit eggs wliich, although they 

 have not been fertilized by the males, are not infertile but produce 

 larvae of the sawfly. This interesting phenomenon, which also 

 occurs in certain other insects, is of importance, as the pro- 

 ductive power of the species is increased when the necessity of 

 the female meeting a male is dispensed with. Shortly after 

 emerging the females begin to deposit their eggs. The eggs are 

 always deposited in the terminal green shoots of the larch and 

 never on any other part of the tree. In laying the eggs the 

 female sawfiy makes an incision in the tender stem of the shoot 

 by means of a pair of saw-like instruments at the end of the 

 body, and into this incision the egg is pushed. The eggs are 

 usually deposited in a double row in the shoot and as many as 

 forty or iifty eggs may be found on a single green shoot. As 

 they are usually deposited along one side of the shoot the in- 

 juries inflicted by the saw-Hke appendages of the female cause 

 the shoot as it grows to curl. In many cases the injuries are so 

 severe as to kill the shoot and the presence of the dead and 

 reddish-brown shoots often serves as an indication of the pres- 

 ence of the insect. In about a week to ten days after deposition 

 the eggs hatch and the young pale-green caterpillars emerge 

 and immediately begin to feed upon the green verticles of the 

 leaves. As they become older they feed in masses, sometimes 

 as many as fifty or sixty caterpillars in a single cluster, and, 

 feeding in this manner, they completely strip the branches of 

 all green leaves which gives the tree a winter aspect in the middle 



