318 MODERN CLASSIFICATION OF INSECTS. 
loop is formed either by an elevated portion of the membrane of the 
strong central vein of the upper wing on its under surface, or by a 
little tuft of raised hairs. This appears to have been first noticed by 
De Geer (tom. i. tab. x. f. 4.) and Harris (in his essay upon the 
membranes of the wings), and afterwards by Giorna (Linn. Trans. 
vol. i. p. 135.) in greater detail. M. Poey (Ann. Soc. Ent. France, 
tom. i.) has observed that the bristle is simple in the males, but 
multiplied in the other sex ; in which, however, according to Kirby 
and Spence, there is no annulus, and consequently these individuals 
are less fitted for flight. See also Hoeven, in Ferussac. Bull. Sci. 
Nat. March 1828. It is chiefly amongst the Sphingide and moths 
that we find this apparatus, the butterflies being destitute of it. 
The legs of these insects are long, slender, and hairy, offering, in 
various species, remarkable peculiarities in the opposite sexes, which 
have not been sufficiently studied. In general the six legs are alike, 
or nearly so; but in some butterflies the fore legs are minute and 
rudimental. The posterior tibiz are often furnished with two pair of 
spurs, namely, a pair at the apex, and another pair below the middle, 
on the inside. ‘This is the case in all the nocturnal and some of the 
diurnal species (forming the family Hesperiidez); whereas the re- 
mainder of the butterflies have only one pair at the apex of the pos- 
terior tibia. The ungues are variable in form, being sometimes bifid. 
In some butterflies, also, they are attended by several curious ap- 
pendages, which have been more particularly described by M. Doyére 
(Ann. Soc. Ent. France, 1837), and figured in the new edition of the 
Rigne Animal, published by Crochard. ‘The abdomen is cylindrical, 
and destitute of a sting; although Dr. Burmeister has noticed an 
exotic species, in the Royal Museum at Berlin, which appeared to be 
provided with an instrument of this kind, but which I should be 
inclined rather to regard as the acute extremity of the ovipositor, 
which, in many species, whose larvee are subterraneous or subcortical 
in their habits, is long and acute. 
Owing to their large size and the greater degree of attention which 
has been bestowed upon these insects, a far greater number of in- 
stances are on record of monstrosities, produced either from accidental 
circumstances in the individual, which is otherwise perfect (as variation 
in size, colour, or markings), or from that imperfect species of her- 
maphroditism which has been termed gynandromorphism, in which 
one individual exhibits portions of the markings or structure of both 
