498 ANNUAL BEPOKT SMITHSONIAN INSTITUTION, 1025 



tinged with pinkish, and the ^ray markings become more restricted 

 and fainter. At this stage the caterpilhir is 11 mm. in length. 



The mandibles of the full}' grown caterpillars are curious in being 

 scarcely tapering, and in having the rounded apical margin armed 

 with four curving clawlike teeth. 



Miss Morion found the larvie after the second molt crawling 

 naked on the limb seeking for fresh supplies of food; she says that 

 then they again si)in a web which they leave after the aphids are 

 consumed. She l)elieve(l that they do not spin a web after the third 

 and last molt; at this stage they go about very quickly. 



Much depends. I believe, upon the size and vigor of the aphid 

 colony. While the fully grown caterpillars are often seen resting 

 in the aphid colonies with the whole dorsal surface exposed, and 

 usually comparatively, sometimes entirely, free from wool so that 

 their handsome nuirkings stand out conspicuously, they may be more 

 or less embedded in the aphids; and frequently, noticing large 

 humps on the surface of the a])hid mass. I have dug out fully grown 

 larvae from flimsy tunnels. Mr. Scudder noted also that some which 

 he obtained remained in the web until readj^ to change into the 

 chrysalis. Except for those just hatched and entering the aphid 

 mass I have seen none but almost or quite fully grown caterpillars 

 exposed, and I think that normally they do not leave their webs 

 until they are ready to pupate. Even though they may not make a 

 covered tunnel I believe the large caterpillars normally and usually 

 spin a path of silk upon the tAvig as thev plough their way through 

 the aphid mass. 



These larger caterpillars are very voracious, and a few of them 

 w411 soon clean out all the aphids in an average alder colony. Where 

 they are common there are always many characteristic ragged white 

 or grayish patches on the twigs composed of the dead remains 

 of aphids entangled in sparsely woven silk, with ragged streamers 

 of silk and dried aphid bodies depending from it. In one locality 

 in Weston, Mass., I observed a number of alder bushes upon which 

 all the numerous aphid colonies had been (juitc exterminated by these 

 caterpillars. 



Mr. Edwards noticed that whenever one of these caterpillars 

 was removed by the forceps a thread held it to the object on which 

 it was resting. He shook his largest caterpillar out of the box 

 until it let out a thread up to a length of 4 inches. Then he held 

 the box to see if the caterpillar would climb the thread, which it 

 did, in about 20 minutes. It twisted its body into a spiral and 

 whirled about so fast that he could not bring the lens to bear, but 

 he could see that the jaws and feet were active. 



I have never seen fully grown caterpillars do this. When dis- 

 turbed they curl up and drop directly down. Small or medium 



