THEIR RELATION TO WEATHER 145 



contagious and frequently kills large numbers of speci- 

 mens. Grasshoppers are often seen dead and dry, on 

 top of some stalk of grass or at the tip of some weed, 

 and this death also is due to disease. When we break 

 up such a grasshopper we find it filled with a powdery 

 mass — the spores of the disease that caused death. 

 Caterpillars are sometimes found presenting a peculiarly 

 limp appearance, and these when touched prove but a 

 pasty mass of bacterial organisms. On a cabbage leaf 

 infested by plant lice we may almost always find a 

 portion that are dull yellowish-brown in color and 

 opaque: victims of disease, easily distinguishable from 

 the parasitized examples which are more distended 

 and somewhat shining or glazed. And so in every 

 order, attacking either larvae or adults, there are dis- 

 eases that lie in wait for them and carry off large per- 

 centages. Some of these diseases have been long known 

 and their effectiveness is so great that efforts have been 

 made to propagate with the view of using them prac- 

 . tically. But it was found that, while some effect was 

 always produced, and while some diseases seemed 

 equally effective year after year, others acted only when 

 weather conditions were just right and were therefore 

 unreliable, because these conditions could not be con- 

 trolled even though the germs of the disease might be 

 supplied. 



The most extensive and most interesting experi- 

 ments of this nature were carried on a few year^ ago in 

 some of the states of the central west against the chinch- 

 bug, which is one of the most serious enemies to grain 

 and com culture in those sections. The chinch-bug 

 is a sucking insect belonging to the order Hemiptera, 

 and therefore cannot be reached by any stomach poison. 

 It is killable by certain contact insecticides, but the 

 task of spraying the enormous grain and com fields 

 10 



