THE CANADIAN ENTOMOLOGIST. 355 



NOTES ON THE PREDACEOUS HABIT OF POLISTES 

 RUBIGINOSUS, ST. FARGEAU. 



BY A. A. GIRAULT, PARIS, TEXAS. 



At 2.30 p.m., Ji-ine 20, 1904, the day clear and warm, I was in a 

 small cornfield near the outskirts of Paris, Texas, searching the ears for 

 full-grown larvse of the cotton boll-worm, Heliothis obsoleta, Fabricius. 

 The infested ears were stripped back or husked, and the full-grown worms 

 taken out, leaving the younger larvse in their places. 



While passing along one of the rows previously examined, a female 

 rubiginosus was frightened and flew up from near the ground, from one 

 of the husked ears attached to a prostrate corn-plant ; she dropped a 

 boll-worm in instar IV. Upon my remaining motionless she returned to 

 the ground near the corn ear, and began to hunt for the larva which had 

 been dropped ; it was in full sight near the ear of corn, but the wasp did 

 not succeed in finding it in the time allowed. In the meantime I had 

 taken one of the full-grown larvae from the box in my hand and placed it 

 on the ear, which it began to attack, working its way down in between 

 the rows of grain. The Polistes crawled over this larva several times in 

 the course of its search for the first one, but without discovering it. 

 Another full-grown larva was then placed on the corn-ear, and crawling up 

 the side of the ear happened to meet the wasp coming from the other 

 direction. The two met on the top of the ear of corn, both moving 

 rapidly, and without the slightest apparent hesitation the wasp literally 

 pounced upon the larva's back, and both rolled to the ground several 

 inches below. 



The boll-worm wriggled and squirmed its body violently, and bit at 

 the wasp fiercely with its jaws, but the latter was more powerful and bit 

 the larva more effectively, making several bad wounds in the ventum of 

 the abdomen, through which a mass of viscera oozed. When thus injured 

 the larva was practically defeated, but the wa?p continued to inflict wounds 

 with its jaws at various points on its body, until it had apparently 

 succumbed. 



The actions of the Polistes thus far indicated nothing more than that 

 it was very hungry and had captured food, and its rapidly-working jaws 

 heightened this effect. However, grasping the limp body of the boll- 

 worm with its jaws and fore legs, and keeping the remaining pairs of legs 

 well spread out for support, the wasp began to girdle the body of the larva 

 by eating or biting (apparently the former) around one of the mid-body 



October, 1907 



