412 ARTICULATES: INSECTS. 



ments, shaping them into hollow rolls and lining them 

 with silk. They generally live in these rolls through the 

 summer, enlarging them as they grow, and carrying on 

 their work of destruction, but in the autumn become tor- 

 pid, change to chrysalids in the spring, and in twenty 

 days come forth winged moths, which in turn lay their 

 eggs for a new brood. 



PTEROPHORII, Latr., OR FEATHER-WINGED MOTH FAM- 

 ILY. This Family comprises moths which have the 

 wings divided lengthwise into narrow-fringed branches, 

 resembling feathers, and the body and legs very long and 

 slender. 



SUB-SECTION III. 



THE SUB-ORDER OF DIPTERA, OR TWO-WINGED INSECTS. 



THE Sub-Order of Diptera comprises insects which have 

 only two wings and two knobbed threads, called balancers, 

 in the place of the hind wings, and a mouth formed for 

 sucking or lapping. The sucker or proboscis is composed 

 of from two to six bristles, in some cases as sharp as 

 needles, and either enclosed in the upper groove of a 

 proboscis-like sheath, terminated by two lips, or covered 

 by one or two laminae, which constitute a sheath for it. 

 They undergo a complete transformation in coming to 

 maturity ; the larvae are without feet, and are called mag- 

 gots, and have their breathing openings generally at the 

 hind extremity. The pupae or chrysalids are in most 

 cases enclosed in the dried skin of the larvae, though some- 

 times naked. Diptera are exceedingly numerous both 

 as regards species and the swarms of individuals of each 

 species. They are mainly small, and many are very 

 minute. In the classification we follow Latreille, with 

 modifications by Westwood, Loew, and others, aided by 

 Loew's Monograph of North American Diptera. 



