INSECT ENEMIES OF WESTERN FORESTS Di 
The adults of cutworms are the dull-colored, yellow, tan, or brown 
moths which collect around lghts at night and are commonly re- 
ferred to as “millers.” They fly at night, usually early in the spring, 
and lay their eggs on the ground where there is ample vegetation for 
larval food. ‘The larvae or cutworms work underground, feeding on 
the roots of various plants, or during the night they often feed above- 
ground on the foliage or clip off the stems at the ground line. They 
are dull-colored, with very few or sometimes no hairs on the body, and 
some have a greasy, slimy appearance that is in keeping with their 
ground habitat. They reach full growth late in the summer or in the 
fall and overwinter in the soil as full-grown larvae or as pupae in 
earthen cells. Emergence takes place the following spring, or in 
some cases there may be several broods a year. 
Clean culture in the nursery to avoid the establishment of weeds or 
ground cover that would be suitable for egg-laying, and cultivation 
in the fall and winter to destroy the hibernating larvae, will do much 
to prevent cutworm damage. Where such methods fail, poisoned 
baits made of bran and white arsenic are effective. A good formula 
for this purpose is as follows: 
Vne mt rane w ee eo oper anew ae LIne eS . 25 pounds. 
NVinitesAEseniGroraparis, Sreen= 222s eee dl fg pS) GAIN MGIC) Se age ey 1 pound. 
RiacksuraMemolassess across Ne ee ae II HS aD C7 LC RD a 
NY BCS a iT pao a 1 to 2 gallons. 
Where seedbeds can be flooded for a time without damage to the 
young trees, cutworms can be drowned. Such treatment is often both 
simple and effective. 
ROOT BARK BEETLES 
Although bark beetles (Scolytidae) are primarily enemies of large 
forest trees, a few species are of importance in killing large seedlings 
through attack on the roots. Species of the genera Hylastes and 
Hylurgops have been found doing this type of damage. Normally 
these are secondary bark beetles which breed in slash and under the 
bark of trees killed by fire or insects, but they appear to be primary 
in attacking the roots of suppressed or weakened seedlings. The 
attacking beetles make entrance burrows at the ground line and con- 
struct winding galleries which extend downward into the larger 
roots and are partly filled with frass. The larvae work through the 
cambium, away from the egg tunnels, and feed together without scor- 
ing the wood. Seedlings an inch or more in diameter are killed by 
the attacks. The species which have been found doing this type of 
damage are noted below: 
Species Hosts 
Wylastes nigrinus Mann =) <= 2.___. Douglas fir, western white pine, western 
hemlock, and probably other conifers. 
TIUIASTCS MGCer AueC ss ete Engelmann spruce, ponderosa pine, and 
lodgepole pine. 
Hylurgops lecontei Sw____---- --- Lodgepole pine, ponderosa pine. 
Hylurgops porosus Lee____------ . Lodgepole pine, western white pine, and 
probably other pines. 
Pseudohylesinus granulatus Lec_. Balsam firs. 
The general habits of bark beetles are more fully discussed in a 
later section (page 96). 
, Ra 7 st SS YE OSes SO OC BRS OMS CORE BREE. 
