332 CONNECTICUT EXPERIMENT STATION REPORT, I907-I908. 



THE HICKORY TUSSOCK MOTH. 

 Halisidota caryae Harris. 



During the past two years this insect has been unusually 

 abundant in Connecticut, and leaves of fruit and shade trees 

 were eaten by the caterpillars. Late in the fall, solitary cater- 

 pillars nearly full-grown were found feeding upon the leaves of 

 nursery, orchard and shade trees. I have not before seen this 

 species so abundant during a residence of nearly fourteen years 

 in Connecticut. 



The eggs are laid early in June on the under side of a leaf 

 in the form of a broad patch about an inch in diameter. The 

 caterpillars are very small and gregarious at first, and may be 

 easily mistaken for the larvae of the fall web-worm or several 

 other species. As the larvae increase in size they take on 

 characteristic markings with eacli molt, until next to the last 

 molting stage they are very striking and pretty caterpillars, being 

 covered with white hairs ornamented with spots of black. Near 

 each end of the body there are two pencils of long black hairs 

 and several tufts of long pure white hairs showing at both ends 

 and along the sides of the body. Plate XV, a. shows this stage 

 of the caterpillars, natural size. In the last caterpillar stage 

 (see Plate XV, b.) the larva has a black stripe on the back, 

 with the four pencils of black hairs as described above. The 

 other hairs are white. The caterpillar is one and one-half inches 

 long, and is very conspicuous and striking in appearance. 



When fully grown it crawls under stones, fence rails, or into 

 some other out-of-the-way corner, and spins a few silken threads, 

 which together with its own hairs form a thin ash-grey cocoon, 

 oval in shape, nearly an inch long and about one-half as thick. 

 The cocoon is shown on Plate XV, c. 



The adult moth measures nearly two inches from tip to tip 

 of wings, and is shown on Plate XV, d. The fore wings are 

 light brown, irregularly spotted with white and with darker 

 lines along the veins. The rear wings are white. 



Wherever the caterpillars are so abundant as to defoliate trees, 

 the proper remedy is to spray with the arsenical poisons, either 

 arsenate of lead or Paris green, according to the formulas given 

 on page 331 of this report. 



