670 



contents are visible through the transparent skin, thus differing from 

 Vesjiamima sequoiae, Hy. Edw., which also infests Douglas fir to a 

 slight extent. This internal dark spot is especially noticeable in one 

 and two-year-old larvae. Pupation takes place in the third season. 

 At high altitudes, an extension of the larval period into the fourth 

 year may occur. In the laboratory the pupal period was 30 days. 

 The general emergence of the moth occurs in June, though some 

 individuals appear as early as the 1st of May and others as late as 

 the beginning of August. The imago lives only about five days after 

 emergence, which accounts for its scarcity. Where there is an 

 abundance of suitable trees for infestation, the female appears to 

 deposit one egg only on each, and thus a number of trees are affected 

 by a single female. Where the insect is abundant, as many as 6 larvae, 

 all of the same generation, have occurred on a single tree. By 

 1st August, the young larvae from eggs laid in June, may be readily 

 located by the boring dust which resembles that of Dendroctonus 

 pseudotsugae, Hopk. At the end of the first active season, a pitch 

 tube covers the wound as well as the larva which made it. During 

 the second season the larva merely maintains and enlarges the tunnel 

 or chamber and it appears to moult for the first time when 1 year old. 

 The third season is passed like the second, the larva again moulting 

 when 2 years old. By the end of this period, the covering pitch-tube 

 is about the size of an American silver dollar. In the third spring 

 the larva is ready to pupate, the adult appearing exactly 3 years after 

 the egg was laid. Although there are no seasons in which this insect 

 is very abundant, there are none in which it is unusually scarce. Unlike 

 others of this group, this insect prefers the shade and is most numerous 

 in from 10- to 50-year-old Douglas firs in spots with a northerly 

 exposure. Larvae under pitch-tubes which are much exposed to the 

 sun, are almost invariably killed during the winter months, as they 

 cannot survive when kept active by warmth, while their food is cut 

 off by frost. A simple and reliable method of ascertaining the localities 

 where this pest is numerous consists of watching the logs at a mill 

 as they go through the saw and noting the areas from which those 

 with pitch seams came. The range of this moth probably extends 

 through the entire native range of the Douglas fir. It also breeds and 

 thrives in wounds on Larix occidentalis (larch), particularly in the 

 pitch flow caused by the fungus, Trametes pini. Larch is not, however, 

 successfully attacked if previously uninjured. The healthier and 

 quicker growing a Douglas fir is, the more it appears to be subject to 

 infestation. Trees are first attacked when 10 years old and are 

 practically immune after they are 50 years old, owing to the bark 

 roughening and thickening. In dealing with the relation of Aegeria 

 novaroensis to other destructive insects, beetles of the genera Melano- 

 phila, Tetropium, etc., are stated to have acted as agents in preparing 

 favourable propagating places for the moth. The rare instances of 

 inter-relation between the latter and Scolytus unispinosus seem of no 

 economic importance. Vespamima sequoia, also infests Douglas fir 

 [see this Review, Ser. A, ii, p. 645], especially in old wounds made by 

 A. novaroensis, thus extending the injury. Wounds in Douglas fir, 

 particularly those made by the pitch moth, are usually infested for 

 several seasons by the larvae of a small species of Ldspeyresia. In 

 localities where A. novaroensis is more than usually numerous, nearly 



