250 



THE AXIHAL EJKGJDOM. 



7. HEMIPTERA (Half-winged). 



The Hemiptera have two pairs of wings, the hindermost 

 small, and the foremost pair half horny and half 

 membraneous, the base being horny, and the apex 

 membraneous. They include the Bugs, some of which 

 are aquatic, as the Water Scorpion (Nepa), and the 

 Water Boatman (Natonecta), which swims on its 

 back, rowing itself by means of a pair of long 

 legs, which look like oars ; the common bed Bug is 

 also of this order, although wingless, as are also the 

 Plant Lice (Aphides), which, however, obtain wings in 

 their perfect state. 



8. DIPTERA (Two-winged). 



The Diptera include the common House Fly (fig. 16), Blue- 

 bottle Fly, Gnat, and many others ; their wings are like 

 the Neuroptera,but they have but one pair, the other pair 

 being undeveloped, form little knobs called " balancers." 



FIG. 29. PART OF GNAT'S WING, MAGNIFIED. 



The wings of Flies are generally covered with short stout 

 hairs, as seen in fig. 29 ; the common Fly feeds upon 

 almost anything, but some of the Diptera feed exclu- 

 sively on the blood of other animals ; the Gnat (Culex 

 pipiens), of which the Mosquito ia a variety, deposits 



