18 BULLETIN 255, U. S. DEPARTMENT OF AGRICULTURE. 
originally made by Sesia novaroensis, thus extending the injury. In 
Montana it infests wounds in the trunks of Douglas fir to the extent 
of about 1 per cent. But in the vicinity of Ashland, Oreg., Vespa- 
mima appears to have developed a special liking for this tree. Fully 
10 per cent of the pitch-moth larvee sent me by Messrs. Edmonston 
and Miller from Ashland proved to be Vespamima sequoia. Accord- 
ing to the accompanying notes, all of the larve of this species were 
collected in wounds previously made. At Placerville, Cal., a single 
larva of Vespamima was collected in Douglas fir, and this was in an 
old wound. 
Wounds in Douglas fir, especially those made by the pitch moth, 
presumably on account of their better protective character, are 
usually infested for several seasons by the larve of a small moth of 
the genus Laspeyresia.1 Two or three larve are frequently found 
around the edges of a single wound. The Laspeyresia also attacks 
young Douglas fir at the base of branches independently, and, 
although the attack itself usually does no permanent injury, the 
resulting accessibility to the cambium often induces infestation by 
the Sesia. That the work of Sesia is responsible for the increasing 
numbers of Laspeyresia, by providing favorable conditions for prop- 
agation, seems a reasonable conclusion, yet it is doubtful if the 
abundance or scarcity of Laspeyresia similarly affects the pitch moth, 
which is well able to establish and sustain itself. 
RELATION TO NATURAL ENEMIES. 
In localities where Sesia novaroensis is more than commonly 
numerous nearly 20 per cent of its larve are killed before reaching 
maturity by a tachinid parasite.2 The influence of this parasite 
as a check on the numbers of Sesia or as lessening the depreciation 
of timber appears from a strictly economic standpoint to be practi- 
cally nothing, since it appears from extensive observations that only 
those moth larve under imperfect pitch tubes are subject to attack 
by the parasite. As the greater number of. pitch tubes form an 
impenetrable barrier against the parasite, there is little reason to 
expect that it will ever be a factor in the control of the pitch moth. 
MEANS OF CONTROL. 
In determining control measures for use against the Douglas fir 
pitch moth five readily accessible areas were selected for detailed in- 
vestigations. On all of these the stand of timber was mixed and the 
conditions were those which obtain in almost any location west of 
the Rocky Mountains, excepting the pure pine stands. The results 
EE ee ee 
1 Identification by August Busck, Bureau of Entomology. 
* Identification by C. T. Greene, Bureau of Entomology. 
