DISEASES OF INSECTS. 207 



Mr. MacLeay, on the authority of M. Clairville, in- 

 forms me) are particularly subject to this disease. But, of 

 all the organs, the wings are most exposed to derange- 

 ments of this kind. De Geer, in a specimen of Pieris 

 Cratcegi just excluded from the chrysalis, observed that 

 one of these was distended by a considerable quantity of 

 extravasated green fluid two or three large drops follow- 

 ing'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 a . Reaumur observed that the 

 wings of some flies were affected by an air-dropsy, as he 

 calls it, which appeared to arise from the air escaping 

 from its natural channels, and thus separating the two 

 membranes that form the wing, and filling the cavity 

 produced by their separation b . 



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 

 only half the length of the other c ; which he regarded 



3 De Geer i. 72. b Reaum. iv. 34.2. 



c Naturf. xii. 224. /. v./ 8. 



