20O THE INTEGUMENTAL SKELETON OF THE IMAGO. 



anterior margin of the wing descends in a semicircular arc, with its convexity 

 behind and its upper limb vertical. During the ascent of the wing the alar 

 apophysis is drawn back, and the axis of the dens is directed backwards and 

 slightly upwards, hence the anterior margin of the wing ascends in a curve, 

 the upper half of which is convex in front. 



When the wing is at rest and flexed, the axis of the dens is nearly 

 horizontal, and the dentate process depresses the patagium and assists in 

 folding the wing. 



The Dens occupies the posterior superior part of the propterygium, and 

 only a small portion of it can be seen externally, the dentate process with 

 the neck and the scale. 



It is apparently represented in the Hymenoptera by two distinct sclerites, 

 the omoplate and signioidea of Chabrier [72, vol. viii., p. 73]. 



The Epaulet (PI. X., c) is a large scale fringed by black bristles, which 

 articulates with the dens behind and with the parascutal plate and the 

 coracoid by syndesmosis ; it covers the sub-epaulet, but does not appear 

 to take any pai t in the formation of the wing-joint, only protecting it in front 

 and above. It does not correspond with the tegula of the Hymenoptera, 

 with which it has been confounded, as this is in front of, and not behind, the 

 anterior spiracle. 



Description of Plate X. 



Fig. I.— The left wing of the Blow-fly. 



Fig. 2. — The roots of the same more highly magnified. 



Fig. 3. — The base of the marginal nervure and of the Remigium of the left wing. 



Fig. 4. — The base of the left Remigium seen from in front and below. 



Fig. 5. — The dorsal aspect of the base of the right Remigium. 



Fig. 6. — The Epaulets of the right winjj, upper and anterior surface. 



Fig. 7. — The left Dens seen from above and in front. 



Fig. 8. — The left Alar Apophysis and Dens seen from the under surface. 



Fig. 9.- — The left Dens seen from the interior of the thorax. 



Fig. 10. — The left Unguiculus seen from behind. 



Fig. II. — The right Unguiculus seen from in front. 



Fig. 12. — The left Parascuta, Dens and Alar Apophysis. 



The following references arc the same in all the figures in wh ch they occur : 

 a, a', apodemes of the pre-epaulet ; aa, alar apophysis ; ap, anterior apodeme, and 

 ap' , posterior apodeme of the remigium ; cr, coracoid ; d, dens ; dp, dentate 

 process of the dens ; e, epaulet ; e', sub-epaulet ; cd, epaulet or .scale of the dens ; 

 /;, hypopterygium ; ha, hamulus ; /', conoid ; /, lobulus ; w, marginal nervure ; 

 mp, metapterygium ; pap, posterior alar apophysis (alar apophysis of the scu- 

 tellum) ; //, posterior, and ps, anterior parascuta ; r, remigium ; s, squama ; 

 s', hy|)opterygial sclerite ; sqa, squaniula ; st, stirrup of the unguiculus ; tb, part 

 of the tympanic bulla ; tm, tympanic membrane ; ti, unguiculus ; «', uncinate 

 process of the anterior parascutum ; A, the deltoid ; T, the tau. Nervures of the 

 wing: m, marginal; /, mediastinal; z, sub -costal; J, radial; 4, ulnar; 

 S, median ; 6, .sub - median ; 7, anal ; <?, axillary ; 9, anterior transverse ; 

 10, patagio-hypocostal ; //, median transverse ; t2, medio-marginal ; /j, discal 

 transverse ; 14, postical transverse ; is, anal transverse. Areas of the wing : 

 a, mediastinal ; /3, 5ub-co.stal ; 7, marginal ; 5, cubital ; i, prepatagial ; 0, sub- 

 apical ; X, apical; /i, discal ; 5, jiatagial ; 0, anterior basal, and x, posterior basal 

 areas. 



