776 REPORT UNITED STATES GEOLOGICAL SURVEY. 



caterpillar resembles the germetrid or measuring-worms in its gait. In 

 this way it can readily be distinguished from either the northern army- 

 worm or the boll-worm. Its body is thickest in the middle, very bairy, 

 green, dotted with black along a subdorsal yellowish line, and with black 

 dots beneath. 



" In Central Alabama," says Grote, " I have watched the growth of 

 the worms on the cotton-plant. The worm appears there in certain 

 seasons, as early as the latter part of June. After feeding for a period 

 of about fourteen days, the cotton-worms commence i)reparations for 

 shedding their skin to pass into the chrysalis stage of growth. For this 

 they spin a few loose threads of silk on the plant itself, which they rarely 

 forsake for that purpose. Within this light web the lost larvaj skin is 

 thrown off, and the brown chrysalis skin is exposed. In this state the 

 worm passes from a week to ten days." 



Eiley states that, "according to the best authority, there are three 

 different broods of worms during the year, the first appearing in June 

 or July, and the last which does the most damage, appearing in August 

 or September, or even later." 



Like our northern army-worm {Lencarda unipuncta), the cotton army- 

 worm, the early stages of the caterpillar having been unnoticed, owing 

 to the fact that it simulates the leaves on which it feeds and is so small, 

 becomes suddenly visible in great numbers in a single day, committing 

 the greatest havoc in a few hours. I extract the following account of 

 an invasion of these cotton-worms, written by Prof. J. Darby, of Auburn, 

 Ala., and quoted in my Guide : " Saturday, September 19, I was in 

 the field examining the forms (buds before flowering) and the young 

 bolls (fruit after the floral organs have fallen off). I examined all care- 

 fully, with no signs of eggs or worms. On Sunday I did not see it. On 

 Monday I passed It as usual and observed nothing unusual. On Tues- 

 day morning I passed it and noticed nothing unusual. On Tuesday 

 noon every plant in the field was stripped of all its upper leaves, not 

 one remaining as far as could be seen, and the iilants were covered with 

 millions of worms. I counted on one plant forty-six worms. They com- 

 mence at the top of the plant, eating every leaf. When the leaves were 

 gone they attacked the young bolls, eating through the perianth and 

 consuming the young cotton. In the course of four days the work was 

 done. They did not touch the grape, nor any other plant in the field. 

 Many left the field and thousands were in the road and on the fences, 

 but not one in a thousand thus escaped. To-day, September 23, there 

 is scarcely one to be seen. Their disappearance is as mysterious as 

 their coming. They have left no signs that I can see, either on the stalks 

 or in the ground. They have extended over hundreds of miles, and 

 nothing ha.s proved a barrier to them, having been as destructive on 

 islands in the river as elsewhere. One-third of the cotton crop has been 

 destroyed. Nothing of the kind has occurred in* thirty years past to my 

 knowledge." 



In 1788 the cotton army- worm destroyed, at a low estimate, 200 tons 

 of cotton in the Bahamas ; in Georgia, the crop was destroyed in 1793, 

 and it was very destructive in 1800, 1801, 1825, and 1820, and since then 

 has been destructive in certain localities nearly each year, though not 

 always in the same State. The average annual loss in this country is 

 probably some years $30,000,000. So great is the annual loss that it 

 would be well if the cotton States would each employ a salaried ento- 

 mologist to investigate and report on the insects injurious to the cotton- 

 plant. The United States Government should also employ competent 

 entomological talent, and have the subject investigated from a broad, 



