ENTOMOLOGY. 27 



the anterior pair of legs imperfect, or not adapted for walking, being too short to reach 

 the plane of position, and usually drawn close to the sides of the thorax, the long hairs 

 of which in a great measure conceal them from our view. These spurious legs have 

 only one joint in the tarsus, which in some cases is without claws j and the species so 

 circumstanced are named tetrapod, or four-footed butterflies. 



The wings are of much greater extent, in proportion to the size of the body, than in 

 any other tribe of insects. The forms which they assume are very various j but the 

 most ordinary shape of the upper pair is triangular, while the outline of the under 

 wings approaches to circular. They are traversed by numerous nervures, which give a 

 great degree of strength to the wing, and hold in tension the thin elastic membrane of 

 which it is composed. 



With such an extent of sail broad-vans, it is easy for butterflies to support themselves 

 for a long time in the air. They seldom fly in a direct line, but advance by rising and 

 falling alternately, in a succession of zig-zags, up and down, and from side to side. By 

 flying in this manner they are supposed to elude more easily the pursuit of the smaller 

 birds, which often make them a prey. 



HELICOPIS GNIDUS. 



No. 1. The wings of the Helicopis Gnidus are white on both sides, with a slight 

 tinge of yellow at the base, and the outer margin black. At the hinder extremity of 

 the secondary wings there is a row of narrow white marks, which is double at the anal 

 angle ; tails black on both sides, the two longest ones tipped with white. The upper 

 wings beneath have a white line dividing the black border behind the middle j and the 

 under pair are ornamented with twenty-one silvery spots, three of which at either ex- 

 tremity are elongated and placed on a white ground, while the rest are insulated, and 

 on a ferruginous ground ; all of them edged with black. 



THAIS MEDESICASTE. 



No. 2. All the species of the genus Thais are of moderate size, and may at once be 

 known by the peculiar design of the coloring of the wings, which are always yellow, 

 spotted with red and black, and bordered externally with a dark festooned line. The 

 palpi are composed of three nearly equal articulations, and rise conspicuously above 

 the head j the antennae rather short, and terminating in a club slightly curved upwards. 

 The body is slender, and the abdominal margin of the hinder pair of wings is curved 

 downwards, as if to leave room for the movements of the abdomen. 



LEPTOCIRCUS CURIUS. 



No. 3. In this genus the head and body are very thick ; abdomen short ; eyes large 

 and salient ; palpi very short, the articulations very indistinct ; antennae rather long, 

 thickening at the extremity into a club, which is slightly curved upwards. The anterior 

 wings are nearly hyaline, and have the discoidal cell closed ; the posterior folded longi- 

 tudinally, and each drawn out into a very long tail, curved at the extremity. The ex- 

 pansion of the wings, in the only known species, is about an inch and a-half ; the inner 

 half of the superior pair black, traversed in the middle by a pretty broad green band ; 



