ENVIRONMENTAL CONSEQUENCES in rocky mountain coniferous ...

Carabids as biological control agents.--Many species of carabids feed on other
insects near, on, or in the ground, as well as larvae that drop to the forest floor
from trees above (Kulman 1974). As such, they effect a certain amount of biological
control against several species of forest insects, including the gypsy moth, Porthe-
- tria dispar (1. ), the eastern spruce budworm, and a species of sawfly.
Kulman (1974) cites earlier investigators who report that in some areas the
ground beetle, Calosoma sycophanta was the most important single control factor of
the gypsy moth. More recently, however, Campbell (1 967) considers that C. sycophanta
probably can be an effective population influencing factor only in areas where dense
host populations have persisted for several years.
Calosoma frigidum (Kearby), is reported as a predator of the eastern spruce
budworm. In two white spruce plantations near Saul t Ste. Marie, Ontario, these large
black carabids were observed crawl ing over the fol iage and eating budworm larvae;
they also seized and ate larvae placed in front of them (fig. 13). A1 though no
quantitative data is available on the impact of these carabids on budworm populations,
investigators (Sanders and Van Frankenhuyzen 1979) feel that the size, numbers,
and manner of searching the current foliage suggests that the beetles may have played
an important role in reducing spruce budworm populations in these two white spruce
plantations.
As a portion bf a larger study of natural enemies of the eastern spruce budworm
(Jennings and others 1979) Reeves and Jennings (1977) are studying carabid beetles
associated with the spruce budworm. One of their objectives is to determine if stand
composition and spruce budworm infestation can be correlated with carabid beet1 e
populations. Other studies show that some species of ground beetles are efficient
predators of spruce budworm larvae that reach the forest floor (Krall and Simmons
1977, 1979). This happens most commonly when a11 the new foliage has been consumed
and budworm larvae spin down to the ground or low vegetation.
In a study of two 'ack pine stands lightly infested with Neodiprion swainei
Midd., Tostowaryk (1973 3 found three species of Pterostichus preyed'to a limited
amount on sawfly cocoons, but the ground beetles preferred Tly puparia. Tostowaryk
(1973) concludes that these carabids are probably only of minor importance in the
control of N. swainei.
Carabids as seed eaters.--Many species of carabids are phytophagous (plqnt
feeders), often feeding on conifer seeds or seedlings. Johnson and Cameron (1969)
list 159 species of Carabidae belonging to 33 genera that are known to use vegetable
matter as food in varying degrees, with some species using it almost exclusively.
Certain genera feed on berries, seeds, tender shoots, and pollen and foliage of
plants (~ssig 1942). Species in the genera Harpalus, Zabrus, Omophran, and Amara eat
cereal and seeds of plants (Imms 1948). Of those specmat use vegetable matter
as food, species in nine genera are known to feed on coniferous seeds and seedlings.
In the northern Rockies, Kennedy and Fell in (1969) found the carabid, Amara
erratica to be the principal insect destroying western white pine seeds afterdirect
seeding in clearcut areas that had been prescribed burned in northern Idaho. They
indicated that spring sowing of seeds treated with Endrin, Arasan, and aluminum
powder prevented carabid damage to seeds. However, Johnson and others (1966) indicate
that "apparently the protective coatings currently in use for reducing seed
losses to birds and rodents have little adverse effect on the ground beetles."
In Washington, Johnson and others (1966) found the carabid, - Amara sp. to be of
minor importance as a seed-eater, but at least six other species of carabids were
found to feed on conifer seed. One species was most abundant in o en areas and
recently logged habitats; another species ate seeds over which bar ! or wood chips had