ir. INSECTA: IIEXAPODA, DIPTERA. 491 



arous females are wingless. At limes winged females appear and spread 



Fig. 528. — Phylloxera vastatrix. (From Ludwig - Leunis.) 1, winged generation: 

 •J, grape root, with nodosities (a) caused by Phylloxera ; 3, wingless root-generation. 



the pests. Winged males appear in the autumn, and the fertilized eggs 

 endure the winter. Of all the species none 

 is more injurious than the PliyUoxera vasta- 

 trix* of the grape, which with us does slight 

 damage, but in Europe has destroyed whole 

 vineyards. This is one of our returns for the 

 many pests the Old World has sent us. 



Sub Order III. APTERA. Wingless bugs 

 with direct development, commonly known 

 as lice, of which three species attack man, 

 one living in the hair {Pedicidus capitis*), 



the others (P. vestimentoram* imdi PlitJiirius Fio. Wi.—Phthirius inguinaiis, 

 ,. J., ii u 1 /-viT ■ crab louse. (After Leuckart.) 



inguinal IS*) upon the body. Other species 



live en other mammals. 



Order IX. Diptera. 



Like the Rhyncliota, the Dijitcra, or flies, are sucking insects, 

 but the sucking tube or haustollum is different, here consisting 

 of a tube formed of both Libium and labrum, and containing 

 stylets which include, besides mandiljles and maxillas (often rudi- 

 mentary), the hypopharynx (fig. 488), the maxillary palpi being 

 present. Only the anterior wings (hence Diptera) are well de- 

 veloped, the hinder wings being replaced by the halteres or lial- 

 ancers, small drumstick-like structures richly supplied with nerves 

 and functioning as organs of equilibration. The thorax is, as in 



