48 THE REPORT OF THE No. 36 



The head was now reddish-black and bore two blunt knobs on top. A section 

 of a larva made the day before the moult shows no evident thickening of the 

 epidermis and underlying tissue. As the insects grew, red lines along the sides of 

 the thorax, a pair of yellow spots and five tubercles of the same colour near the 

 anal end of the uplifted abdomen could be made out.. By the time the larvae were 

 8 mm. long they were eating both surfaces of the leaves and when feeding arranged 

 themselves along the cut edges. Hairy warts on the head, and dorsal and lateral 

 spines on the body gave the insects, which could now be seen from above, a rather 

 unattractive look. When not feeding the larvse placed themselves in rows on the 

 stem and bared veins of the leaf. 



The numerous two-winged flies which were seen on the leaves of neighbouring 

 apple trees, did not seem to notice the colonies.. One larva dissappeared at this 

 stage — perhaps, to the nest of one of the wasps which were decorating the cornice 

 of a near-by room. 



After the second moult the head became black again and remained so until 

 the final moult. The various tubercles and spines were more marked and the 

 insects, which were at this time denuding the branch, eating even the veins and 

 midrib of the leaves, could now be seen at a distance of six feet. Numerous insect- 

 eating birds hopped about on the near-by trees and some stopped to examine the 

 colonies. A young song-sparrow disposed of one larva, but the other six which 

 disappeared during the third and fourth stages succumbed to the heavy rains which 

 were of frequent occurrence last August. 



At the final moult the larvae developed the coral-red head and large abdominal 

 hump of the same colour which gives them the common name of the Red-Humped 

 Apple Worm. During the last days of the fourth stage I took a number of larvae 

 from the control colony that I might make sections of them and follow the changes 

 which immediately precede the final moult, but my time has been so taken up that 

 I have not yet examined them. 



During the last stage the larvae increased in size from 20 mm. at the time of 

 the fourth moult to 30 mm., which they attained before descending the tree to 

 pupate. Although they were conspicuous objects which could easily be made out 

 at some distance, the birds did not molest them. 



My colony of Heterocampa larvae were hatched from a few eggs that were laid 

 by a female caught at night. By means of a smear of gum I attached the eggs to 

 the under surface of a red maple leaf. On the eighth day the larvae emerged and 

 began feeding on the superficial tissues of the leaf. They were then about 5 mm. 

 long and under a glass showed nine pairs of comparatively enormous horns. The 

 first pair on the prothoracic segment were four-tined like the antlers of a deer, the 

 remaining eight pairs were single-pronged. Section of the insect shows the horns 

 to be pure dermal structures devoid of muscle. On the fourth day the larvae 

 moulted and lost all trace of the horns except a pair of short stumps on the pro- 

 thoracic segment. 



During the first stage no enemies seem to have discovered these larvae, but on 

 the third day of the second stage while I was absent in the country they all dis- 

 appeared. Some predaceous insect probably got them, for they were well hidden 

 from the birds. 



The individual larvae of these species experience no change of surroundings 

 which might call for an abrupt change in colour or armament. They pass their 

 whole larval existence on the tree upon which the parent moth deposits the eggs, 

 indeed, they do not leave the branch, unless compelled by lack of food, until they 

 all, in regimental order, descend the tree to pass the winter as pupae beneath the dry 



