366 REPORT UPON COTTON INSECTS. 



In all of these tables care was taken to count only those larva} which were so small 

 that there was every probability of their having been hatched on the leaf where 

 they were found ; and the tables were prepared at the time when most of the eggs for 

 the fifth brood had been laid and a few were beginning to hatch. 



From an examination of the first table it appears that on this plant there were three 

 and a half times as many eggs (including the young larvae) on the middle third of the 

 plant as on the other two-thirds combined. 



The second table shows that the eggs were more evenly distributed on the second 

 plant examined than on the first, yet the middle third bore more than the rest of the 

 plant. 



It may be seen from the third table that on the third plant the distribution of the 

 eggs was still more uniform, and here the number on the middle third is intermediate 

 between that on the other two-thirds, the larger number being found on the bottom 

 third of the plant. 



Averaging the three.tables, we find that there are 20 eggs for the bottom third of a 

 plant, 34 for the middle third, and 14 for the upper third. The middle third averages 

 as many as the other two-thirds taken together. 



On the first plant those leaves which bore eggs at all averaged 2.7 per leaf, on the sec- 

 ond plant 1.7, and on the third plant 1.5. On the three plants the average number is 

 1.9 eggs per leaf. This, I think, may fairly be taken as representing the abundance 

 of eggs in the section where my observations were made, for the first plant was an 

 average representative of the field in which it grew, and the caterpillars were very 

 abundant there. The second was taken from a field where there were fewer worms, 

 and the third was taken from a field where there were very few caterpillars before the 

 fifth brood appeared, so that the eggs counted were nearly all deposited by moths 

 which had come from other fields. 



Oviposition being dependent upon the instinct of a living animal and not upon nat- 

 ural laws, figures like these will not enable us to predict where any individual moth 

 will lay its eggs ; but as instinct is pretty constant with insects they may be taken as 

 showing what commonly occurs. 



Of several hundred eggs that I examined, probably not a half a dozen were laid on 

 any part of the cotton-plant but the lower surface of the leaves. Most of these were 

 deposited on the lamella of the blade, a very few on the veins. Two or three were 

 found on the upper surface of the leaves ; one was seen on the peduncle or flower- 

 stalk, about one-eighth of an inch from the base of the flower ; and two were noticed 

 on the outer surface of the involucre around the flower. As a rule they were not laid 

 close together, yet once or twice two were found almost in contact. 



Under natural conditions, late in summer, I found that the eggs of Aletia usually 

 hatch in the course of the first four days after being deposited ; but the time required 

 seems to vary according to the temperature, as 1 found that some hatched in about two 

 days, while others that were taken into the house required upwards of a week, and a 

 considerable number blacken and never hatch, from some cause that I was unable to de- 

 termine. After the exclusion of the larva the eggshell is of a gray or whitish color, and 

 sometimes remains adhering to the leaf for a considerable length of time ; after it has 

 been removed there is often a faint impression to be seen where it was attached to the 



When first hatched, the young larva feeds on the parenchyma of that surface of the 

 leaf on which it chances to find itself, and it is not till it is from two to four days old 

 that it perforates the cuticle on the other side of the leaf. The first direct signs of 

 the caterpillar are, therefore, transparent places of small extent and more or less 

 rounded outline, on the larger leaves of the plant. Why this epidermis should be left 

 uneaten I am unable to say ; but as the larvae are usually hatched on the lower sur- 

 face of the leaf it appears that this habit may be due to an instinct teaching the larva 

 to preserve this screen against the rays of the sun Avhile it is very young. That it is 

 an instinct seems to be shown by the fact that larvae hatched on the upper surface of 

 the leaf, in confinement, ate the parenchyma from this surface and left the cuticle 

 untouched on the lower side. Though small places are often found where young 

 larvae have eaten the lower side of the leaf without perforating the epidermis, while 

 the larvae cannot be found, I have no evidence that a caterpillar ever leaves the leaf 

 on which it was born till it is old enough to eat through it ; and in the cases just men- 

 tioned I believe that the larvae have been removed by some predaceous animal. 



Having reached the age of three or four days, many larvae go from the tough leaves, 

 where they have passed the early part of their existence, to the tender leaves near the 

 top of the plant and the ends of the branches, and, eating the substance of these leaves 

 from between the veins, which are left intact, they honeycomb or rag them, and this 

 is generally the first sign of their presence that is noticed by planters, though when 

 they are sufficiently numerous to make this honeycombing very noticeable a peculiar 

 odor is perceived in the cotton-field, which seems to be due not only to the crushing of 

 the leaves by the mandibles of the caterpillars, but to the large quantity of excre- 

 ment which they void, and which, from the rapid passage of their food through their 



