104 PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



plant, and consequently its death through starvation, an accomplished 

 fact had its abundance not been reduced through the prevalence of a 

 disease superficially similar to the "wilt" of the gipsy moth. 



The fall webworm is generally a common and abundant insect in 

 New England,, but rarely as common or abundant as it frequently 

 becomes in the South. An elaborate study of its parasites and the 

 effect which parasitism apparently played in effecting its control was 

 made in the fall of 1910, with interesting results. It was found that 

 the prevailing percentage of parasitism was sufficient to offset an 

 increase of no less than fourfold annually, and even at that there is 

 reason to believe that our results err on the side of conservatism. 

 The elimination of these parasites for a very short period of years 

 would undoubtedly be followed by an increase of the host comparable 

 to that of the gipsy moth. 



The one insect studied at the laboratory which appears habitually 

 and under its normal environment to become so unduly abundant 

 as to invite destruction through disease at regular intervals is the 

 tent caterpillar. 



In the report upon its parasites, 1 it was contended that they played 

 a part subservient to that taken by the disease, and this statement 

 drew forth some criticism at the time of its publication. It is a 

 satisfaction to note that the original contention appears to be upheld 

 by the results of studies conducted at the gipsy-moth parasite labora- 

 tory. These results seem to justify the further contention that the 

 present status of the tent caterpillar is, in a way, prophetic of that 

 which would result were the gipsy moth to be left to the control 

 of its disease. 



At frequent but irregular intervals the tent caterpillar increases 

 to such an extent as to become a pest, and unless artificially checked 

 it defoliates fruit trees in southern New England. That it never 

 reaches the destructiveness characteristic of the gipsy-moth invasion 

 is seemingly due to difference in habit. As is well known, the gipsy- 

 moth caterpillar is almost an omnivorous feeder and the female moth 

 is incapable of flight. Its eggs are deposited indiscriminately in 

 every conceivable place to which a caterpillar or moth can gain 

 access. The adult of the tent caterpillar is in no way restricted to 

 the immediate vicinity of the locality where it chose to pupate as a 

 caterpillar, but, instead, uses what really amounts to an unwise 

 amount of discretion in its selection of a place for oviposition. 

 Cherry first and then apple is selected in preference to all other food 

 plants, and with the exception of a limited number of other rosaceous 

 trees and shrubs, its eggs are almost never found elsewhere. As a 

 result, when it is at all abundant its caterpillars, which have not the 



1 Technical Bulletin 5, New Hampshire Agricultural Experiment Station. 



