78 REPORT UPON COTTON INSECTS. 



that, as a rule, this insect lives at that season thirteen days as a larva, 

 before webbing up, and remains as a larva one day after this, before 

 changing to a pupa. Occasionally, two days elapse between the web- 

 bing up and the change to pupa. Specimens which were kept in breed- 

 ing-cages in my office remained eighteen days in the larval state. This 

 unusually long time was probably due to the fact that the temperature 

 of the room in which they were kept was much lower than that in the 

 cotton-fields. Specimens bred by Professor Glover under similar circum- 

 stances passed twenty days before webbing up.* 



The larva sheds its skin five times during the period of its growth. 

 The individuals which I bred moulted at regular intervals of three days, 

 the first moult being made when the larvae were three days old. At 

 this moult nearly all the larvae ate their shed skins. During the first 

 stage the head of the larva is marked only by the six black eyes on either 

 side. After the first moult the conspicuous black spots on the head 

 appear. When six days old the larvae moulted the second time, and 

 when nine days old the third moult occurred. At this moult the larvae 

 began to vary in color ; some becoming striped with black, and others 

 remaining green. On the twelfth day the fourth moult occurred, and 

 the fifth moult on the fifteenth day. Three days later the larvae webbed 

 up. When full grown the larva measures If inches in length. A de- 

 tailed description of the full-grown larva is appended to this section. 



The variation in color referred to above is quite interesting ; no expla- 

 nation of it has been discovered. I found by experiment that the dis- 

 tinction is not a sexual one, as moths of each sex were bred from each 

 kind of larvae. General observations, that is, those made without abso- 

 lutely counting the individuals of each color, show that there are no 

 dark larvse in either the first or second broods. About one-fourth, or 

 less, of the third brood are striped with black. About one-half, or 

 slightly more, of the fourth brood are dark, many of them being almost 

 entirely black; while nearly all of the fifth brood, "third crop" of the 

 planters, are black or very darkly striped. 



After the larvae become large enough to eat through the leaves, or, in 

 the language of the planter, "to rag the cotton," they move to the top of 

 the plant and destroy the tender terminal foliage; thus the earliest indi- 

 cation usually observed of the presence of the worms is the "ragging" 

 of the tops of the plants. As already stated, this has led to the practice 

 of " topping" the cotton. 



In feeding, the worms rest upon either the upper or lower surface of 

 the leaf, but more frequently upon the latter. They eat most early in 

 the morning and late in the evening. As we have frequently observed 

 with other caterpillars, the cotton worm may often be seen resting upon 

 some portion of the plant, supporting itself by its prolegs and swinging 

 the anterior part of its body from side to side as if fanning itself. The 

 larva has another interesting habit. When touched or otherwise fright- 

 * Agricultural Report, 1855, p 75. 



