THE DEAGON-FLIES. 199 



which is apparently destitute of palpi, and composed 

 of a central piece, sometimes cleft down the middle, 

 and two lateral lobes, the whole forming a broad 

 plate, which completely closes the mouth from be- 

 neath, but doubtless from its mobility assists greatly 

 in the engulfing of its owner's unfortunate prey. 

 The prothorax forms a slender collar immediately 

 behind the head, but the other two segments of the 

 thorax, which bear the large, equal, and finely reticu- 

 lated wings, are of large size, and laid upon each 

 other obliquely, so that the point of insertion of the 

 hind legs is considerably in advance of that of the 

 posterior wings. The legs are of moderate length, 

 and slender, with the thighs and tibiae armed with 

 small spines, and the tarsi composed only of three 

 joints. The abdomen is always long and slender, 

 sometimes prismatic in its form, sometimes cylin- 

 drical ; in the males it is often terminated by peculiar 

 appendages, which are employed in a curious way 

 during the amours of these creatures. 



One of the largest and most abundant of the 

 British species of this tribe is the IMellula depressa, 

 an insect well known to schoolboys under the deno- 

 mination of the "horse-stinger," an appellation to 

 which it can certainly lay no just claim. It measures 

 about two inches in length, and nearly twice as much 

 in the extent of its large, powerful, transparent wings, 

 which are divided into a multitude of small, square, 

 and pentagonal meshes by fine black veins, marked 

 at the base with an opake reddish patch, and with a 

 small black stigma near the apex on the anterior 

 margin. Its general colour is a dingy yellow, varie- 

 gated, especially on the thorax, with lines of a brighter 

 tint and black; the abdomen is rather broad and 



