XII] 



ORDERS OF INSECTS 



257 



Order XL Hemiptera. 



The Hemiptera . (Gr. i}/u, half) have mouth-parts arranged for 

 piercing and sucking. The basal part of the labium is elongated 

 and tubular and the mandible and first maxilla form sharp pointed 

 styles. The two pairs of wings may be alike or may differ and 

 the anterior pair are in some cases half horny and half membranous. 

 The metamorphosis is incomplete, there being no quiescent stage. 



The members of this order present very great divergence both 

 of form and of size ; they are colloquially known as Bugs and Lice. 

 Amongst the commoner forms are the Water-boatman/JVbfowecta ; 

 the Water-scorpion, Nepa ; the Bed-bug, Acanthia ; the Cicada, 

 the " Cicala " of Italy, remarkable for its chirping noise ; the Frog- 

 hoppers, including the Cuckoo-spit, Aphrophora ; the Plant-louse, 

 Aphis; the Phylloxera, which destroys vines and Scale Insects from 

 one of which the dye Cochineal is prepared. 



Order XII. Diptera. 



The Diptera (Gr. 8t-7TT6pa, two-winged) 

 have mouth-parts arranged for piercing and 

 sucking. The chief difference in this 

 respect from the Hemiptera consists in the 

 fact that the sucking tube is partly formed 

 by the labrum and that the first maxillae 

 retain palps. In addition to the styles formed 

 by the elongation of the mandibles and the 

 laciniae of the first maxillae there is a fifth 



style, the hypopharynx, situated 

 middle line which represents an 

 elongated chin and carries the duct 

 of the salivary gland. Only one pair 

 of wings, the anterior, are present ; 

 the posterior are represented by a 

 pair of short knobs called balancers 

 or halteres (Fig. 112). The meta- 

 morphosis is complete. 



The Diptera or Flies form one 

 of the largest of the Insect Orders, 

 probably as large as the Coleoptera, 

 although at present the number 

 of species of Beetles named and 



S. & M. 



Ill 



the 



FIG. 111. Glossina mor~ 

 sitans, the Tsetse-fly. 



FIG. 112. Cecidomyia destructor, 



the Hessian-fly. 



1. Insect. 2. Larva. 3. Pupa, 

 or "flax seed." All magnified. 



17 



