232 
Dr. Kidd- on the 
correct, though probably it has ere this been corrected by 
himself, a statement made by Cuvier in his Regne Animale, 
Tom. iii. p. 126, that in the myriapoda there are twenty stig- 
mata and upwards ; but in all other insects eighteen at most. 
He also asserts in the same place, that insects respire by two 
principal tracheae extending longitudinally, one on each side 
of the body, from which other tracheae ramify. Now cer- 
tainly in the gryllotalpa, and, as I have reason to believe in 
many other insects also, the longitudinal tracheae bear so 
small a proportion in their capacity to the aggregate capacity 
of the other tracheae, that in such instances they cannot be 
called principal tracheae. My own opinion is, that these 
longitudinal tracheae serve as connecting channels, by which 
the insect is enabled to direct the air to particular parts, for 
occasional purposes. 
Though not immediately bearing on the present point, I 
beg leave here to state a fact which I have not seen else- 
where noticed, that in the two segments of the body which 
carry the middle and hind pair of the true legs, in the larvae of 
coleopterous and lepidopterous insects, there are no stigmata, 
discernible at least either to the naked eye, or a common 
magnifying lens. 
But, to return to the stigmata of the gryllotalpa, the first 
in order beginning from the head, is situated very near the 
lower part of the posterior ridge of the thorax. This stigma, 
not to object to the term in the present instance, is apparently 
connected with all the tracheae both of the thorax' and of the 
head itself. It differs remarkably in size and form from all 
the rest ; for instead of being a mere dot or point, it is an 
elongated fissure, bounded by two horny lips. The second 
stigma, which somewhat resembles in form, though of much 
