200 DISEASES OF INSECTS. 
beetle and not on the other. Those of Serropalpus (as 
Mr. Macleay, on the authority of M. Clairville, informs 
me) are particularly subject to this disease. But, of all 
the organs, the wings are most exposed to derangements 
of this kind. De Geer, in a specimen of Pieris Crategt 
just excluded from the chrysalis, observed that one of 
these was distended by a considerable quantity of extra- 
vasated green fluid—two or three large drops following 
an incision. This disease appeared to arise from the 
lower membrane not adhering to the upper; so that the 
nervures—which are rather longitudinal channels, being 
open below, than tubes—were not closed to confine the 
fluid to its proper course. The malady, which might 
be called a dropsy of the wing, carried off the insect 
the day after its exclusion?. Reaumur observed that 
the wings of some flies were affected by an azr-dropsy, 
as he calls it, which appeared to arise from the air escap- 
ing from its natural channels, and thus separating the 
two membranes that form the wing, and filling the ca- 
vity produced by their separation». 
Sometimes also monstrosities are to be met with in 
these animals, or variations from a symmetrical structure 
in organs that are pairs. I have a beetle in which the 
terminal joint of one of the maxillary palpi is short, ovate, 
and acute; and that of the other, long, semiovate, and 
rather obtuse. A specimen of Blaps Mortisaga in my 
cabinet, taken by Mr. Denny, besides the terminal mucro 
of the elytra, has a long diverging lateral one. Goeze 
had the larva of a Semblis brought to him in which one 
of the two fore-legs, though perfect in all its parts, was 
a . G - entare 
De Geer 1. 72—, » Reaum. iv. 342. 
