APPENDIX I REPORTS OF OBSERVERS. 367 



bodies, is only partially digested. When there are not very many caterpillars they do 

 no more than to partly eat these upper leaves, excepting early in the season, when few 

 leaves are expanded and the cotton-plants are very small, when a single larva has 

 then been known to completely defoliate two or three plants. When more abundant 

 they eat all of the parenchyma from between the veins of these leaves and rag the 

 lower leaves to a certain extent ; and when very numerous they reduce every leaf on 

 the plant to a mere skeleton, consisting of the stronger veins, besides eating up the 

 flowers and flower buds* and the involucres or "squares" from about the bolls, 

 while frequently they eat large irregular holes in the half -grown bolls, and sometimes 

 go so far as to gnaw the bark from the stem of the plant. 



When there are enough caterpillars to eat the entire foliage from a plant those 

 which are not full grown migrate in search of food on other plants, while those already 

 grown seek some kind of leaves in which to transform to pupae. Thus it happens that 

 after a large field has been eaten out one may see thousands of larvae of all sizes crawl- 

 ing in .every direction over the ground. At night most of these, larvae ascend the cot- 

 ton-plants near which they chance to be, and remain quiet till the next day, when 

 their search is renewed. This is the only marching that I observed, t 



The natural food of Aletia larvae appears to be only the leaves of the cotton-plant, 

 at least in this country. Though they were seen to eat bracts, calyx, corolla, stamens, 

 and pist.ils of the cotton-flowers, as well as the walls of the boll and the half-grown 

 seeds which it contained, and even the bark of the plant, as stated above, they were 

 never seen to feed upon any other plant. Larvae of various sizes were several times 

 transferred from cotton to three other malvaceous plants, but they remained on them 

 a very short time, and did not attempt to eat their leaves. Confined in breeding jars 

 with leaves of these plants they preferred starving to feeding upon the food given 

 them ; and the only time that I ever saw one attempt to eat anything but parts of the 

 cotton-plant was when one of these ate a very little parenchyma from the lower sur- 

 face of an okra leaf. 



A strange peculiarity of this species is the variation in color which occurs in its dif- 

 ferent broods of larvae thus : up to the middle of July no larvae were found which 

 were not of a light green color ; but of what the planters call the " first crop " in July 

 I found a small percentage to have black or dark brown dorsal stripes. Of the " sec- 

 ond crop," in August, about one-half were dark striped, some of them possessing lat- 

 eral stripes, so that they appeared almost entirely black ; and by far the greater part 

 of the " third crop," in September, were very dark. Several larvae, of next to the last 

 brood, were reared from the egg in dark boxes in the house, so that the only light 

 which they received was once or twice a day, when their boxes were opened a few 

 minutes to change their food leaves. At first they were green, though with a cloudy 

 appearance ; but as they grew older they became striped with black, so as to resemble 

 tile darkest larvae of the preceding brood. This shows that the direct action of light 

 is not needed to produce this color change, and that it is a progressive change, keeping 

 pace with the growth of the larvae. What its physiological importance is I am unable 

 to say4 



In August, when the fourth brood of larvae were at work, I saw many of them eating both the 

 petals of flowers and the entire contents of unopened flower buds, though there were plenty of leaves 

 still remaining on the planta. 



t In talking with planters I find that many of them apply the name " army-worm " to this species 

 in seasons when its later broods appear in great numbers in places where no signs of the earlier broods 

 have been seen. Their numbers are sometimes so large that two or three days suffice for them to strip 

 the foliage from thousands of acres of cotton where no signs of the worm had been previously noticed. 

 "When there are enough of them to do that there would be a sufficient number crossing the roads 

 about the field to give the impression of an army in motion, though there might be no system to their 

 marching. 



JSome facts bearing on this subject of larval coloration have been collected by Sir John Lubbock 

 (Scientific Lectures, London, 1879), but they do not suggest to me an explanation of the present case. 

 He says, (page 49): " In various genera we find black caterpillars, which are of course very conspicuous, 

 and, sj> far as I know, not distasteful to birds. In such cases, however, it will be found that they are 

 covered with hairs or spines, which protect them from most birds. In these cases the bold, dark color 

 may be an advantage, by rendering the hair more conspicuous." Though Aletia is somewhat hairy. I 

 doubt if its coating is much of a protection, and I did not notice that the hairs were more conspicuous 

 on the black than on the green larvas ; on the contrary, I believe that they are less apparent as seen 

 against the black background of the insect's body. Sir John finds that of sixty-six British butterfly 

 larvae, " ten are black ; and, as we have already seen, all these are spiny or hairy." When speaking 

 of the linear markings of caterpillars (page 45), he says: " It is important that there should be certain 

 marks to divert the eye from the outlines of the body. This is effected, and much protection given, by 

 longitudinal lines, which accordingly are found on a great many caterpillars. These lines, both in color 

 and thickness, much resemble some of the lines on leaves (especially those, for instance, of grasses), 



and also the streaks of shadow which occur among foliage. If, however, this be the explanation of 

 them, then they ought to be wanting, as a general rule, in very small caterpillars, and to prevail most 

 among those which feed on or among grasses. * * * But yon will find that the smallest caterpillars 

 rarely possess these white streaka. As regards the second point also, the streaks are generally want- 

 ing in caterpillars which feed on large-leaved plants. * * * In fact we may say, as a general rule, 

 that these longitudinal streaks only occur on caterpillars which live on or among narrow-leaved plants." 

 As I have stated, both the production of the linear marks and the change in the ground color in Aletia, 

 are progressive as the larvae increases in size and age, but so far as I know these larvae never feed on 



