THE COLEOPTERA 



115 



iityrusJj. (Fig. 105), about two and one-half inches long, is greenish-gray 

 with black spots on the elytra. The male has a long horn on the head, 

 projecting forward and upward, and another projecting forward from the 

 pronotum. The female has only a small tubercle on the head. It occurs 

 in the Southern States. In another species found in the West the pro- 

 thoracic horn is much longer. 



Fig. 105. — Rhinoceros Beetle {Dynastes tityrus L.), about mituial size. {Original.) 



Family Chrysomelidae (Leaf beetles). — This is the largest family of 

 beetles but its members are small, not often being over half an inch long. 

 Most of them are leaf feeders, though the larvae of a few are worm-like 

 and attack underground stems or roots. Many are serious pests, and 

 though almost none are found throughout the entire country, allied species 

 working in similar ways, occur. 



In the group as a whole, yellowish elytra with black lines or spots 

 seems to be the prevailing color pattern, though of course, with many 

 exceptions. Together with the next two families, from which other 

 characters separate this one, the third segment of the tarsus is generally 

 broad, being drawn out into a lobe on each side, and is covered beneath 

 with minute, closely set hairs (pubescent). The antennae are at most, 

 of only average length. 



The Colorado Potato Beetle {Leptinotarsa decimlineata Say). — 

 This well-known insect was discovered about 1823 by Long's exploring 

 expedition to the Rocky Mountains, in the region of the upper Missouri 

 River. Its food there was the Buffalo-bur (Solanum rostratum Dunal) 

 and the insect was apparently not remarkably abundant, and certainly 

 of no economic importance, nor did it become so until civilization, and 

 with this the potato, reached that territory. Then a new and satis- 

 factory food plant, abundant enough to provide all the insects with food 

 became available and the potato beetle increased in numbers and began 

 to spread to the East. At first its rate of spread was only about 50 

 miles a year but after crossing the Mississippi River this became more 

 rapid and it reached the Atlantic Coast about 1874. Since then it has 

 spread both northward and southward until it is now found practically 



