124 NATURAL HISTORY OF INSECTS. 



GROUSE-LOCUSTS (Tittiginse). This group contains insects 

 of a small size, in which the upper part of the thorax is pro- 

 longed backward nearly to the tip of the abdomen, and some- 

 times beyond it. 



TRUE LOCUSTS (Acridinx). In this group the upper part of 

 the thorax extends but little, or not at all, upon the base of 

 the abdomen (Fig. 89 ) . This group contains the more promi- 

 nently injurious species, such as those which migrate in 

 swarms in immense numbers. 



CHAPTER XIX. 



FAMILIES OF NEUROPTERA. (Dragon-Flies, May-Flies, etc.) 



WHITE ANTS (Termitidse). These insects are provided with 

 four wings of equal size; the antennae are conspicuous, and 

 the feet are four-jointed; transformations incomplete. The 

 common White Ant is of a yellowish-white color, and is 

 occasionally injurious to growing trees by gnawing the bark 

 near the roots, but is more often met with in decayed wood. 



FUNGUS-FLIES (Psocidse). These insects are usually provided 

 with four wings (Fig. 144), of which the hind pair is the small- 

 est; in some, however, all the wings are rudimentary, in 

 others, entirely wanting; the feet are from two to three- 

 jointed; the antennae are conspicuous; transformations in- 

 complete. These insects usually feed upon dry vegetable 

 substance, especiallv upon lichens, and a few kinds are injuri- 

 ous to collections of Natural History. 



PERLA-FLIES (Perlidas). These insects have four wings of 

 equal size, else the hind wings are the broadest; all the wings 

 are sometimes rudimentary; the antennae are very long, and 

 the feet are three-jointed; in many species there are two long 

 bristles at the posterior end of the abdomen; transformations 

 incomplete. The larv of the greater number of these insects 

 are aquatic. 



MAY-FLIES (Ephemeridsi). The insects belonging to this 



