180 REPORT UPON COTTON INSECTS. 



(Prodenia autumnalis of Riley), Mr. Glover, in the Department of Agri- 

 culture Report for 1855, p. 78, says : 



The grass-caterpillars, when in confinement, very often kill and devour each other, 

 and when one is maimed in the least it stands a very poor chance for its life. Several 

 intelligent planters state that when the grass and weeds are entirely devoured, and 

 no other vegetable food is to be found, they will attack each other, and feed upon the 

 still living and writhing bodies of their former companions. One grass-caterpillar 

 which was kept in confinement, although furnished with an abundance of green food, 

 actually appeared to prefer to feed upon other caterpillars, no matter of what kind, so 

 long as their bodies were not defended by long bristling hairs or spines. 



It is in the next order, HYMENOPTERA, that we find the most effective 

 enemies of the cotton-worm. 



WASPS (Hymenopt., fam. Vespariae). These well-known insects, as a 

 class, although they occasionally do some harm by injuring fruit or by 

 killing honey-bees, may, on the whole, be called very beneficial insects. 

 Not only do they devour injurious insects themselves, but they also 

 store them up as food for their young. Concerning the actions of cer- 

 tain wasps in the cotton fields, we cannot do better than to quote again 

 from Mr. Trelease's report : 



Wasps freqnent the cotton plant in considerable numbers, being attracted, like the 

 ants, in part by the nectar secreted by the plant ; and there is much reason to believe 

 that all of the species which visit the plant feed more or less commonly upon the 

 caterpillar or larva of Aletia. I am led to this conclusion by the following observations. 

 On the 8th of August, when larvae of the fourth brood of Aletia were very abundant 

 in the swamp-cotton, I saw a large red and yellow wasp Polistes bellicosa, Cresson 

 (see Fig. 34) hunting for them. Carefully walking around the holes eaten through 

 by the caterpillars, she explored their borders with 

 her antennae, as if feeling for the larvae ; and each 

 time that she found one in this way she quicklysprang 

 after it, but at the same instant the larva threw itself 

 from the leaf; so that, while I was watching her, I 

 saw no less than eight escape, the ninth being caught 

 and eaten. Occasionally she would stop hunting 

 long enough to sip a little nectar from the foliar glands 

 of the plant, and then the chase was resumed. I 

 was very much surprised to see that she relied eii- 

 FIG. 34. Polistes bellicosa. tirely on the tactile sense of the antennae for finding 

 her prey. Though possessing well-developed ocelli and compound eyes, she seemed to 

 make little use of them ; and repeatedly I saw her alight on a leaf close to a caterpillar 

 without paying any attention to him till she touched him with her antennas, when, as 

 before stated, she would instantly spring after it. Observations of this sort were made 

 several times on this wasp. Another large brown wasp (I'olistes sp.) was also seen to 

 catch larval Aletias, as also were a yellow-jacket hornet ( J'espa sp. ), and r. common mud- 

 dauber ( Pelopceus caruleus, Linn. ), and they all alternated hunting for cateridllan; with 

 feeding on nectar. Both species of Folistes were several times seen flying about with 

 dead caterpillars, having previously reduced them to a pulpy mass with their man- 

 dibles. They were probably looking for some quiet place in which to eat them. 



Further on in the report occurs the following : 



Early in September, while watching these moths as they fed on rotting figs, I saw 

 many white-faced hornets ( Vespa maculata) about the fig-trees. One of these hornets 

 was seen to catch a two-winged fly nearly as large aa itse'-f. After killing it, the hor- 



