HEXAPODA : DIPTEKA OR FLIES, ETC. 

 FIG. 403. 



313 



Silk-worm Moth, Bombyx mori. 



FIG. 404. 



Fio. 405. 



Tent-Caterpillar Moth, Clisiocampa ameri- 

 cana, Harris. 



Cocoon of Tent-Caterpillar, C. ameri- 

 cana, Harris. 



" 3. THE SUB-ORDER OF DIPTERA is so named from the fact 

 that the insects of this group have only two real wings, 

 the place of. the hind wings being supplied by two knobbed 

 threads called balancers, as seen in Figs. 406, 410. The 

 name is from the Greek dis, two, and pteron,. a wing. 

 The mouth of the Diptera is modified for either sucking 

 or lapping. The sucker or proboscis is composed of two 

 to six bristle-like organs, in some cases sharper than the 

 sharpest needles, and either inclosed in the groove of a 

 sheath terminated by two lips, or covered by one or two 

 lamime which serve the purpose of a sheath. 



The Dipters undergo a complete transformation in 



coming to maturity. Their larvse are without feet, and 



are called maggots. The pupae in most cases are inclosed 



in the dried skill of the larvae. Some kinds of dipters, as 



14 



