250 NATURE STUDY AND LIFE 



The smaller ichneumons (of course there are distinc- 

 tions other than size) are now called "braconids," and the 

 smallest, many of them not more than one one-hundredth 

 of an inch in length, have been set apart by themselves as 

 the Chalcis flies. 



The Braconids. — One of the commonest braconids is 

 parasitic on the tomato sphinx. Others are found on the 

 grape sphinx and the cabbage worms. Little bunches of 

 white or yellow cocoons, often found attached to grasses 

 and weeds, if preserved in a bottle covered with gauze, 

 will be found to contain insects of this family. 



One of the most 

 interesting of these 

 little parasites for 

 the children to study 

 belongs to the genus 

 Aphidius, so named 

 from its work with 

 the plant lice. If colonies of aphids are examined late 

 in the season, from July to October, many will be found 

 lighter colored than the rest and much swollen. Often 

 an artichoke leaf or a spray of yellow dock will have a 

 dozen or more such specimens. Keep a number in a glass 

 covered with gauze, and within a few days you will find 

 neat little trapdoors cut in the backs of the aphids and 

 the minute parasites flying about in the glass. Let them 

 have golden-rod or asters and a fresh supply of plant lice 

 in a window or large gauze cage and see who can observe 

 them laying their eggs. Another similar parasite of the 

 aphids emerges from the plant louse when it reaches 

 maturity and spins a flat cocoon, using the shell of its 



Fig. 104. P'AUASiTizED Plant Lice 

 (Photograph by the autlior) 



