8 CIRCULAR 2 41, U. S. DEPARTMENT OF AGRICULTURE 



proportions from a trace to 80 per cent. Considering only these 

 species, there were only 770 out of about 28,000 stomachs examined 

 (about 1 in 36) which contained leaf -hopper remains, and in the 

 majority of cases the leaf -hopper material amounted only to from 1 

 to 10 per cent. But including all species of birds, out of about 47.000 

 stomachs examined these 770 would be less than 1 out of 60, so on a 

 most liberal estimate only about one-tenth of 1 per cent of the food 

 of birds can be said to be leaf hoppers. 



Later records showed 1,435 stomachs out of about 80,000 to con- 

 tain leaf-hopper remains. These represented 175 species, and of 35 

 of these species the remains were found in 10 or more instances. In a 

 number of cases from 20 to 50 leaf hoppers were found in a single 

 stomach, and in one instance, that of a barn swallow, about 1,000 

 were found. It may be concluded, however, that the previous state- 

 ment that birds are practically a negligible factor in the control of 

 these pests holds true. This does not, however, affect the conclu- 

 sions as to the value of birds in destroying other kinds of insects, 

 especially such larger forms as grasshoppers, cutworms, army worms, 

 and sod worms. 



SPIDERS 



The great abundance of spiders in pastures, meadows, and grain 

 fields is often most manifest by the immense number of webs that 

 may be seen, especially on dewy mornings. These webs, however, tell 

 only part of the story, as there are a great many species of jumping 

 and running spiders which construct no webs to capture their prey, 

 and among these there are to be counted some of the most numerous 

 and active insect feeders of the fields. These spiders are often taken 

 in large numbers when sweeping for leaf hoppers, and that they feed 

 readily upon the hoppers is proved by finding them with hoppers in 

 their grasp within a few seconds after their capture in the net. 

 Direct observation on unconfined individuals is difficult, since both 

 spiders and leaf hoppers are so hard to watch, but enough has been 

 seen to justify the opinion that spiders are among the most widely 

 distributed, constant, and effective agents in keeping leaf hoppers in 

 check. 



A very extensive study of the food of spiders has been made by 

 Bilsing (£, p. 232), in which he found that spiders were very effective 

 in capturing leaf hoppers, and that they occur in such large numbers 

 as to be a very important factor in the reduction of the numbers of 

 these as well as other insects. In mentioning one particular species, 

 a common meadow spider, Agelena naevia Walck., he says: 



The number of these spiders in any given area is enormous. In order to 

 determine how numerous this spider is, I counted them on several different 

 areas. In a clearing which was full of stumps and brush piles and which is 

 an ideal place for this spider, I counted them in midsummer when most of 

 them were nearly full grown. On an area of two and one-half acres, nine 

 hundred and thirty-four individuals were counted. On a brush pile six feet 

 in diameter, I counted thirty-two of these spiders. Another count was made 

 along a lane for a distance of one hundred and thirty-two feet, the count being 

 taken on both sides of the lane between the ditch and the fence. In this 

 distance there were two hundred and sixty spiders. 



Spiders therefore may be considered as a very important and 

 fairly constant factor in the reduction of leaf hoppers and their 

 presence in the fields as of distinct advantage. 



