78 CEREAL AND FORAGE INSECTS. 



On August 24, 1909, 12 nearly full-grown caterpillars were counted 

 upon a single square foot beside the road from Cimarron to Springer. 

 Near by, in a C. S. ranch pasture, 1 square rod gave a count of 196, 

 or over 20,000,000 to the square mile. August 30, in another pasture, 

 two miles from this last count, an area of average infestation showed 

 126 to the square rod. 



By a very conservative estimate, the total infested area in 1909 was 

 at least 15,000 square miles. It may have been much greater. With 

 an average of 10 caterpillars to the square rod (a conservative esti- 

 mate) the total number of the pests would reach 1,536,000,000. The 

 investigations of the past two years would seem to show that nearly 

 all the caterpillars reach the adult stage. Supposing that two-thirds 

 become moths, there would be a billion moths, more than one-third 

 of which would be females, each capable of depositing from 100 to 150 

 eggs. A little calculation will convince anyone of the tremendous 

 possibilities for harm which the figures given above involve — figures 

 that have not been made at random, or hastily. 



In connection with the vast numbers of these caterpillars their 

 size must also be borne in mind. The full-grown larvae frequently 

 measure 2 J inches in length, with the diameter of a man's index 

 finger. When moving about for food they give an observer the 

 impression of being larger then they actually are. Where they are 

 so numerous that one really has to choose his steps to avoid crushing 

 these huge, spiny, ugly caterpillars at every move, the sensation 

 produced by them is peculiar and lasting, especially after walking for 

 miles through their myriads. 



FATAL EFFECTS OF HEAT ON LARVAE. 



The extreme sensitiveness of the larvae of Hemileuca to the heat 

 of the sun's rays was often noticed, and a series of experiments was 

 undertaken to learn if this tendency to avoid the sunlight arose from 

 fear or merely from dislike. Numbers of individuals of varying ages 

 were at different times placed on smooth bare ground that had been 

 heated by the cloudless sun to a warmth that was disagreeable to the 

 bare hand. As no thermometer was within reach the exact tempera- 

 ture could not be ascertained. The larvae invariably showed signs of 

 distress, almost at once, and began to scramble as rapidly as possible 

 for the nearest shelter. In some cases they would die before moving 

 an inch, and only in rare instances did any survive where the distance 

 to be traversed equaled 24 inches. Larvae of the fourth and fifth 

 stages showed greater vitality and could travel farther than smaller 

 forms, but even they would always succumb to the sun's heat if 

 compelled to remain on the hot earth for a fraction of a minute. 



July 5, 19 third-stage larvae were placed on the earth 12 inches 

 from the nearest shelter. Several collapsed almost instantly, scarcely 



