ii8 INSECTS 



it of voluntary motion, is said to seize it by an antenna 

 and lead it into a sheltered spot before it deposits the 

 egg. The roach simply stays where it was led until 

 the wasp larva kills it by feeding. 



This method of stupefying prey is a very high 

 specialization and the stinging is by no means a hap- 

 hazard one. The wasp seeks the thoracic ganglion of 

 the nervous system of adult insects, and may sting' 

 several ganglia in caterpillars, to make them entirely 

 quiet. The poison introduced is said to resemble formic 

 acid in composition and to act as a preservative as well 

 as a paralyzing agent. But this preservative effect 

 has been disputed and there are yet many interesting 

 points to be elucidated in the biology of these predatory 

 wasps. The number of specimens collected and stored 

 by them is very little appreciated, but it is enormous, 

 and the reduction in the number of specimens thus 

 preyed upon forms a very important factor in the 

 check to undue increase. 



The social or paper-making wasps are also feeders 

 upon insects; but not so exclusively, and they make 

 no store of food for their larvae. They feed the young 

 from day to day with prepared food, chewed into proper 

 condition by the nurses, and consisting partly of insect 

 fragments and partly of plant juices. 



Ants destroy many insects, but do not usually 

 make specific war upon any one species. They are 

 very apt to attack, kill and eat almost any sort of 

 helpless creature that they find, but few of the species 

 of the temperate zone feed largely enough upon insect 

 food to form a notable check to any species. 



Several families are exclusively or almost exclu- 

 sively parasitic, and these range in size from forms 

 so small as to be scarcely visible to the untrained eye, 

 to specimens expanding two inches or more, with ovi- 



