290 IKJUEIOUS INSECTS 



person, on comparing the beaks of the two, will never 

 mistake one for the other. Another way to distinguish 

 the injurious ones from our friends, is by the disagreeable 

 odor given off by the former, while the beneficial ones, so 

 far as I know, are free from the odor. 



The two-winged flies — order Diptera — furnish the agri- 

 culturist with but few directly beneficial insects, and 

 these are the pretty, bright-colored Syrphus flies, and 

 the dull-colored, parasitic Tachina flies. But there are 

 many that act the part of scavengers while in the larva 

 state — as the house and flesh flies — while others are very 

 annoying, as the mosquito and horse-flies. 



In the order Orthoptera, including grasshoppers, crick- 

 ets, cockroaches, etc., we fail to find any that are useful 



Fig. 171.— lAOB-WINOED CHRTSOPA. 



to man, and so pass them by and stop at the last order, 

 Neuroptera, where nearly all are carnivorous. These 

 insects are called nerve-winged, because the veins in their 

 wings look like net-work. The Mosquito Hawk or 

 Dragon-fly is a good example of this order, as are also 

 the pretty little Lace-wing flies (Chrysopa), seen in figure 

 171 in all their stages. The larvae of these Lace-wings eat 

 the Plum Curculio and the Pear Slug, and probably many 

 other noxious insects. The eggs of the Lace-wings are 

 each attached to a long foot-stalk, and all fastened to a 

 leaf or blade of grass, as seen at a, figure 171. The per- 

 fect insect, d, is a pretty, pale-green, gauzy-winged crea- 

 ture, with prominent, shining, golden eyes. 



