368 REPORT UPON COTTON INSECTS. 



When resting upon the leaf, or feeding, the larvae are often very restless. When 

 disturbed, the smaller ones allow themselves to drop from the leaf, first taking the 

 precaution to attach a silken thread to it so that they can arrest their descent or as- 

 cend at will. The older larvae, under similar circumstances, hold the posterior half of 

 their bodies to the leaf by means of their prolegs, while they quickly sway the ante- 

 rior half from side to side. If further disturbed or sometimes even at the first they 

 throw their bodies from the leaf, alighting on a lower leaf in many cases, but some- 

 times falling to the ground. The young larva runs away from its enemy ; the older 

 one tries to frighten him at first, but, failing in this, runs away afterward. It is in- 

 teresting to notice that while larvae often escape from winged enemies such as the 

 wasps, by exercising this saltatory power, they often ensure their quick destruction 

 by using this same power when attacked by ants, for when once the ants have got a 

 larvae that they are attacking on the ground his fate is certain. 



In feeding, I find that the larvae rest either on the upper or lower surface of the 

 leaf, but more frequently on the latter. They have been found on the upper surface 

 eating ravenously, though exposed to the rays of the midday sun, when the land in 

 which the cotton grew was so heated that caterpillars which fell from the plant onto 

 it were killed by the heat in a few minutes ; but as a general thing they seem to eat 

 most early in the morning and late in the afternoon. A few have been seen eating 

 after dark, but when examined during the night most of them appeared to be lying 

 quietly on the leaves. 



When about twelve days old, the larva of Aletia draws a leaf about its body, fasten- 

 ing it with a yellowish silk spun from near its mouth. This process is known to plant- 

 ers as " webbing up." In the course of the next twenty- four hours its body shortens 

 and increases in diameter, assuming a somewhat fusiform shape j those parts which 

 were light green become bluish or of a copperas color ; and finally it sheds its skin and 

 becomes a pupa. This is at first invested in a delicate green membrane, but in a few 

 hours its color begins to change to a brown, which sometimes becomes so deep as to ap- 

 pear almost black ; and this change in color is attended by a toughening and hardening 

 of its body wall. When a larva has webbed up in a leaf on the cotton plant it often 

 happens that other larvae eat the leaf from about it, and if there were not some special 

 provision the pupa would then fall to the ground. But nature has provided for such 

 a contingency by giving it a set of hooks at its sharp or posterior extremity, and these, 

 catching in its web, anchor it to the plant. Still, when thus exposed, the pupae must 

 suffer more from their natural enemies, and especially birds, than when concealed by a 

 leaf; hence, probably, the instinct which prompts many larvae to leave the plant on. 

 which they had fed and web up in the leaves of the cow-pea, morning-glory, grass, or 

 other plants growing in the cotton-field, while there may be plenty of uneaten leaves 

 on the plants which they desert. In July and August I found that the pupa state 

 lasted usually about ten days, though quite often it would reach fifteen, seeming to be 

 influenced by the temperature. At the end of this time the skin of the pupa is rup- 

 tured, and through the opening thus formed the moth emerges. Though neither eat>- 

 ing nor possessing the power of locomotion, the pupa of Aletia can vibrate its body 

 rapidly as it is suspended from its web by its anal hoo ks after the leaf has been eaten 

 from about it ; and this, like the similar motion of the larva, probably serves to 

 frighten away some of its enemies. 



When the moth emerges from the pupa shell, its wings are wet and useless, and if 

 it be then approached it can escape only by running, aided by a sort of hopping, ia 

 which its wings assist it a little. But in a short time the superabundant fluid dries 

 from the wings, and they assume the form characteristic of the perfect insect, and are 

 then used in flight. How long the moths live when unconfined I have no means of 

 knowing, but in breeding-jars I have found that those of the third and fourth broods 

 die within five days after their exclusion from the pupa. 



Both larvae and pupae being sexually imperfect, the duty of reproducing the species 

 devolves upon the moths ; and these consist of males and females, which copulate, the 

 females lay their eggs, and all die soon after. I could not determine how soon alter 

 their exclusion these moths usually copulate, and only once did I see anything that 

 looked like coition, while oven then what I observed may not have been copulation. 

 The facts are as follows : While watching a large number of moths collected about a 

 jujube-tree, on the fruit of which they feed, and which I had illuminated by a lantern 

 hung on one of the branches, I often saw one moth dart at another in its flight, hover 

 over it, and appear to come in contact with it, the whole lasting only a second or two, 

 .after which they separated and flew away in different directions. In my breeding- 

 jars, when kept supplied with fresh cotton-leaves, the female moths began oviposition 



anything but the cotton-plant, the leaves of which are broad and not linear like those of grasses. Fi- 

 nally, "as Weissniann points out, wo may learn another very interesting fact from those caterpillar*. 

 They leave the egg, as wo have seen, a plain ereen, like so many other caterpillars, and gradually 



, 



acquire a succession of markings. The young larvae, in fact, represents an old form, and the species, 

 in the lapse of ages, has gone through the stage which each individual now passes through in a few 

 weeks. Thns, then, the individual life of certain caterpillars gives us a clew to the history of the spe- 



