ENTOMOLOGY IN OUTLINE HYMENOPTERA. 



113 



above and two below, joined together; near the end they are toothed 

 like a saw, and between them is the egg passage. In the larger species, 

 the females seem possessed of a special sense by which they ascertain 

 whether their victim has already been attacked. If it contains an egg, 

 they abandon it for another. This, for the reason that the food supply 

 would not be sufficient for two lar^e larvae. With the smaller species, 

 however, it is not uncommon for the female to lay a number of eggs 

 on one victim. But it is not alone in their larval stage that insects 

 are attacked by parasites, for they are subject to it at any stage of their 

 existence, from infancy to age. Even in the egg, they are not immune, 

 for there are egg parasites minute insects, which lay their eggs within 

 the eggs of other insects, which are eaten out by their internes. 



The family Stephanidse contains a few r rare insects of no importance 

 in this discussion. 



The family Braeonidse, however, is a different matter, for this is a 

 very extensive family of, generally, very small to medium sized insects, 

 containing several thousand described species. All are parasitic on 



other insects, and in this we 



find many of the secondary 

 and tertiary parasites. This 

 family, in the older classifica- 

 tions, is included in the Ich- 

 neumonidse, but well-defined 

 differences in the two classes 

 have led to the creation of the 

 new family of Braconida?. As 

 parasitic insects, however, 

 their habits of life are very 

 similar, and to their efforts is 

 largely due the fact that we 

 are not entirely eaten out by 

 the destructive pests. One of 

 the chief checks on the aphids 

 of our gardens is a minute 

 member of this family, the 

 genus Aphidiu*. Examine *a 

 twig or leaf infested with 

 plant-lice, and you will see 

 many of them bloated and 

 white. Look closely and you 



will see a minute circular hole in the abdominal end. It is from this 

 hole that the insect, after having eaten out the aphis, and gone through 

 all its changes on the inside of the victim, has escaped. Gather a few 



8-E 



FTG. 110. Tomato-worm (Phlegethontius sexta), bear- 

 ing cocoons of the parasitic Apanteles congrcfjaitm. 

 Natural size. 



