40 INSECTS INJURIOUS TO STATLE CROPS. 



observer will luirdly be able to diftijiguisli from other 

 families of the group. Bat it will be noticed that the fine 

 yeius of the wings vary considerably in the different jDara- 

 sites figured, and it is by these that the entomologist is 

 enabled to separate the different groups and often to 

 identify the species at a glance. Both this and the fol- 

 lowing family are 2)eculiar in having an exceedingly long 



Fig. 21.— a Plant-louse Fiu-nnite (Aphidius gr-inaj'iaphis), showing 

 above the parasitized louse from which it has issued. (Copied 

 from J. B. Smith ) 



ovipositor or egg-tube, of which it will be seen that they 

 make a very good use. It is with this extensile tube that 

 the female deftly punctures the skin of some unsuspecting 

 caterpillar, and under it inserts her eggs. In a few days 

 there hatch from these a host of young grubs, which feed 

 npon the Juices and tissues of the caterpilhir, but are 

 seemingly careful to avoid injuring any of its vital organs, 

 for as soon as the caterpillar reaches its full growth it 



