18 

 THE COTTON WORM.* 



The life of the cotton worm is divided into four distinct periods or 

 stages, wkich always occur in the same order. There can be no change 

 of sequence and it is impossible for any stage to be L f t out. The four 

 stages are the egg, the larva, the pupa and the adult. 



While the egg of this insect is small and perhaps not commonly 

 known, yet every one knows the nature and function of an egg, and 

 in these respects the cotton worm egg is like all other. It is small, 

 rounded, greenish in colour, and v\hen seen with a lens shows fine 

 radiating lines upon its upper surface, 



The eggs are laid on the under surface of the cotton leuf and are 

 scattered about, not in clusters. 



The larva is more commonly called the caterpillar or worm. The 

 last of these names is incorrect, because tl e caterpillar of a moth or 

 butterfly is in to sense a worm. The name cotton worm has, however, 

 became so well established that it seems advisable to retain it rather 

 than to attempt to change it, thereby perhaps creating great con- 

 fusion. 



The skin of a caterpillar is not capable of much growth after i; once 

 becomes hardened. In order, therefore, to increase its size to the full, 

 it is necessary for the animal to shed its skin several times, each new 

 skin being much larger than the preceding. The new skin is already 

 developed under the old one, and is very soft but soon becomes dis- 

 tended and firm. At the last of these ' moults' or changes of the skin, 

 instead of another caterpillar skin, a dark- brown thick covering is de- 

 veloped, the body is much shortened and the pupa oi chrysalis appears. 



Some insects roll up leaves or spin silken coc ons previous to the 

 last moult in which to pass the pupal period The cotton worm gene- 

 rally ties over merely an edge of the leaf, i hough sometimes, if suit- 

 able cover is not at hand, the pupa is formed almost without cover 



In the pupa stage the wings, mouth-parts and antennae of the adult 

 are developed, the reproductive organs being perfected from mere rudi- 

 mentary forms. At this time the insect does not feed and has no 

 power to move from place to place, its only power of motion being ti 

 wriggling or twisting movement, which is frequently noticed when 

 the pupa is disturbed. 



When the necessary changes have taken place within the dark- 

 brown pupa skin, it breaks open and the adult insect crawls out At 

 first its wings are very smnll but they quickly spread out, and in .1 

 very short time the small, olive-grey moth is dry, its wings strong 

 and it is able to fly. The caterpillar has strong biting jtiws audit 

 swallows its food in solid particles, but in the moth the mouth-parts 

 are so changed that no jaws are to be seen, but instead a long slender 

 thread-like proboscis, by means of which it sucks up the nectar from 

 flowers. 



In this stage the insect does no dt mage to the cotton plant, merely 

 sucking up enough of the nectar from the flowers and the nectar glands 

 of the leaf to keep itself alive while performing the reproductive func- 



♦ Ccmmiinicated by ihe Imperial Department of Agriculture for the West 

 Indiea. 



