84 THE REPORT OF THE No. 19 



this reason, their injuries were not of such a serious nature as they would 

 have been had the habits of the larvae been different and the outbreak occurred 

 in June or early in July, when the trees were making most growth. 



The caterpillar of the Hickory Halisidota and that of the Spotted Halisi- 

 dota are very different in appearance. The body of the former is clothed 

 with dense tufts of white hairs, with a ridge of black hairs down the centre 

 of the back, and two pairs of long black pencils on the 1st and 7th abdominal 

 segments, while that of the latter is covered with tufts of bright yellow and 

 black hairs, the black tufts being on the four anterior and three posterior 

 segments and the yellow tufts on the remaining segments. The latter are 

 centered down the middle of the back with a row of black spots. The larva 

 of the Hickory Halisidota is slightly the larger of the two, measuring when 

 full grown about an inch and a half in length. 



Both caterpillars are general feeders, being known to attack a great 

 many different kinds of plants. At Ottawa, we have found the larvae of 

 both species chiefly on elm, basswood, alder, willow, oak and ash. In his 

 "Insects Affecting Park and Woodland Trees," Dr. E. P. Felt says that in 

 New York State the caterpillars of the Hickory Halisidota show a decided 

 preference for walnut, butternut and sumac. The larva of the Spotted 

 Halisidota Tussock Moth is chiefly recorded as an oak-feeding species, in fact 

 it is referred to by some writers as the Oak Tussock Caferpillar. When dis- 

 turbed, both of these larvae have the habit of falling to the ground and curl- 

 ing up, in which position they may remain for some little time. 



When these two kinds of caterpillars become full grown in autumn, 

 they wander about in search of suitable places to make their winter homes, 

 and when such are found each larva spins an oblong oval cocoon composed 

 of the hairs from its body. The cocoons of both species are of the same size, 

 averaging a little over | of an inch in length by about J an inch in width. 

 They are different in colour, however, and owing to this can be easily separ- 

 ated. Halisidota caryce has a cocoon of a uniform ashy gray colour, while 

 the cocoon of Halisidota maculata is of a decided yellow, from the bright 

 yellow hairs from the larva showing up among the black hairs, also from the 



Fig. 28. The Hickory 

 Halisidota Tussock" Fig. 29. The Spotted Halisidota 



Moth . Tussock Moth . 



body of the caterpillar. In some specimens of the latter the yellow is more 

 intense than in others, this of course being caused by more than the usual 

 number of the vellow hairs on the larva. At the present time these cocoons 

 can be readily found in open woods, etc., under pieces of old plank, dry logs, 

 or evpu stones. On October 8th of the present year, I collected 13 cocoons of 

 the Hickory Halisidota, fastened to the underside of a small piece of board. 

 This was near a large basswood tree on which the larvae had been feeding. 

 Many other cocoons occurred near by. 



• Soon after completing its cocoon the caterpillar changes to a reddish- 

 brown pupa, the moths emerging the following June. The Hickory Halisi- 

 dota Tussock Moth (Fig. 28), measures when the wings are expanded from 



