ARTHROPODA. 121 



Order VI. DIPTEEA. 

 ANTLIATA. 



Wings two, membranous, never folded, with radiate nervures; 

 posterior wings replaced by a small clavate filament on each side 

 [halteres]. A suctorial proboscis. Prothorax very short. Me- 

 tamorphosis complete. Larva apodal. 



In this order the proboscis is composed of mandibles, maxillae, 

 and a central piece or tongue [glossarium], the labium, often 

 with a fleshy terminal lip, serving as a sheath, and they are often 

 converted into chitinous setae or into lancet-shaped bodies. 

 There are commonly two maxillary, but no labial palpi. The 

 antennae are in general very short, of three joints, the last fur- 

 nished with a bristle ; in the Nemocera the antennae are jointed 

 in the ordinary manner. The eyes are large, and there are three 

 ocelli. The pro- and metathorax are much reduced, and the 

 mesothorax correspondingly enlarged. The wings have often a 

 membranous appendage at the base [alula] ; there is also fre- 

 quently a small scarious scale [squamula] placed behind the 

 insertion of the wings. The halteres are attached to the meta- 

 thorax ; they have been supposed to be subservient to respiration, 

 to hearing, and to smell. The abdomen in the female is some- 

 times terminated by a sort of telescopic ovipositor. The foot, 

 besides its two claws, is provided with two, rarely three, cushions 

 [pulvilli], covered beneath with fine hairs, expanded at their 

 tips, supposed to act as suckers, probably aided by the secretion 

 of a viscid matter. 



Many of the Diptera are useful scavengers in the larval state, 

 but others are very injurious e. g. 'Cecidomyia destructor to 

 wheat-ci*ops, Tipula oleracea to grass-lands, JJacus olece to the 

 fruit of the olive, &c. In the perfect state they are too often 

 pests to man and beast, sucking the blood, or depositing their 

 eggs in or on their bodies, causing tumours, ulcerations, and 

 death. 



