On Gnats' Scales. 193 



the proboscis of the Gnat ; and indeed no one would expect to 

 find so curious a departure from the ordinary characteristic of the 

 order Diptera as that presented by the Cuhcidte. Francis Walker, 

 F.L.S., mentions in his ' Insecta Britannica,' 1856, that the veins 

 of the wings of Culex, Anopheles, Coretkra, Mochlongx, and Aedes, 

 "are fringed with scales," but he omits to notice their occurrence on 

 other parts of the insects. As both Gennan authors and American 

 translator have repeated my error of the " wavy appearance " of 

 the scale, and made sundry other slight mistakes, it may be as well 

 to enter a little more fully than I have hitherto done into the 

 structure and variety of " Gnats' scales." 



Scales are a generic characteristic of the Cuhcidfe, and although 

 presenting pretty much the same appearance differ essentially in 

 form. There are four distinct kinds : the proboscis, palpi, and legs 

 are entirely covered over with the battledore scales, represented at 

 Fig. 1. The nervures or venations of the wings, and portions of 

 the body of the insect, have regularly arranged rows of scales, shown 

 at Fig. 2 ; while from the marginal edges of the wings project 

 slender scales, which terminate in a point. Fig. 3. The intennediate 

 portions of the wings and body are covered with fine hairs, the 

 thorax with tufts of feathery scales somewhat peculiar in form, 

 Fig. 4, the pedicles of which are considerably longer than the rest, 

 while the upper part gradually widens out and terminates abruptly 

 in a crenated edge. These may be briefly described as trumpei- 

 slia]^ed scales. In each case the scale is inserted by a narrow 

 pedicle into the chitinous membrane, gradually assumes a scutiform 

 appearance, and terminates in a crenate or pointed edge. The base- 

 ment membrane is homogeneous, and the upper layer is corrugated 

 or traversed by longitudinal ribs, and these again are regularly and 

 finely striated throughout in the horizontal plane. It is the stria- 

 tions on the ribs which, when seen slightly out of focus, give to the 

 scales a wavy appearance. 



It is curious to find portions of C. 2nptens completely clothed, 

 and other parts free from scales. The legs are covered throughout, 

 as shown in Fig. 5, and the feathers seem to take the place of hairs 

 in other famihes of the Diptera. The proboscis, which is half the 

 length of the male insect, is used as a prehensile organ and as 

 a sheath or scabbard to the exquisitely-formed set of j)enetrating 

 instruments. A slender needle-like piece, seen in the drawing, Fig. 6, 

 just projecting out of the sheath, is serrated towards the tip, and 

 thickened at the back hke a scythe. It is said to be employed as a 

 suctorial apparatus, or, when the insect is irritated, for conveying 

 a fluid which is thought to be poisonous, from the minute receptacle 

 situated at the base of the proboscis. The feathered sheath can, 

 by a Httle careful dissection, be drawn off' the slender set of instru- 

 ments. To secure perfectly good scales, and preserve them in an 



