DISEASES OF INSECTS. 209 
subject to vertigo, which has been attributed to their 
eating poisonous honey a — but may not this disease in all 
these cases arise from some derangement of the nervous 
system ? One of the ants which was so affected had lost 
one of its antennae ; but as this was not the case with the 
others, no great stress is to be laid upon the circumstance. 
Huber does not inform us whether those attacked by 
this disease recovered or not. 
I have observed more than once, that \hejlesh-jly and 
some others of the same tribe are subject in particular 
seasons to a kind of convulsions. When thus attacked, 
they kick and struggle, and seem unable to fly. Some- 
times they lie upon their backs without motion, but if a 
finger be placed near them their convulsive motions are 
renewed. When thrown into the air, instead of flying, 
they fall to thegi-ound. Had this distemper occurred ear- 
lier or later in the year I should have attributed it to the 
benumbing effects of cold ; but as my observations were 
made one year (1816) in May, and in another (1811) in 
the latter end of June, this could scarcely be the case. 
In the year last mentioned I observed that many flies 
died under its influence. In wet seasons this tribe is 
subject to another disease, which proves fatal to many of 
them, and indeed to other Diptera. A white crust ap- 
pears to be formed upon the abdomen both above and 
below, of a granular appearance, much resembling fine 
moist sugar. On the back of that part this crust does 
not cover the margins of the segments, which gives it 
the appearance of white bands ; so that deceived by it, I 
have often at first flattered myself that I had met with 
* .V. Did. d'llist. Nat. i. 42. 
VOL. IV. \ P 
