Il6 A MANUAL OF FORESTRY 



particularly in early spring, they can then be cut off and 

 burned. The species is killed also by spraying with arsenical 

 mixtures. The range of this insect is similar to that of the 

 gipsy moth, but is more widespread, extending farther west and 

 north. 



THE LARCH SAWFLY (Nematus erichsonii}. 



This insect is distributed through the range of the tamarack, 

 on the leaves of which it feeds. Complete defoliation often 

 results from the attack of the sawfly, and the tamarack over a 

 large region may be killed. In the early 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 life history of the insects 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 sawfly is that it can reproduce parthenogenetically; this 

 means that the females can deposit eggs which, 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 sawfly 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 



