208 DISEASES OF INSECTS. 
as a reproduction, but it seems rather a malformation. 
Miiller mentions a most extraordinary fact of one of the 
Noctuida, which when disclosed from the pupa retained 
the head of the larva a . One of the most remarkable 
instances of this kind that have fallen under my own 
observation, may be seen in a specimen of Chrysomela 
hamoptera in the cabinet of our friend Curtis ; in which 
one of the thighs produces a double tibia, but only one 
of these is furnished with a tarsus. 
The diseases of insects which arise from some internal 
cause are not very numerous. The first that I shall 
mention is a kind of vertigo. " Ants have also their 
maladies," says M. P. Huber : « I have noticed one ex- 
tremely singular; the individuals attacked by it lose their 
power of guiding themselves in a straight line, they can 
walk only by turning round in a circle of small diameter 
and always in the same direction. A virgin female shut 
up in one of my glasses was seized on a sudden with this 
distemper ; she described a circle of an inch in diameter, 
and made about a thousand turns in an hour, or not 
quite seventeen in a minute. She continued constantly 
turning round for seven days, and when I visited her in 
the night I found her still in motion. I gave her honey 
— and I think that she ate some of it." He observed 
that some workers were attacked by a similar disease : 
one of these, however, had the power of walking from 
time to time in a straight line ; when placed upon its head 
it continued its gyrations b . Similar motions of a little 
moth, mentioned on a former occasion , may perhaps 
have been produced by the same cause. Bees are also 
•> Naturf. xvi. t. iv.f. 1 — 3. h Huber FoUrmk, 174. note 1. 
c Vor.. II. p. 365. 
