62 INTERNAL ANATOMY OF INSECTS. 



laminated structure shows itself very clearly in old spe- 

 cimens, and in such as have been immersed in boiling 

 water 3 . 



ii. Trachea and Bronchia*. Parallel with each side 

 of the body of most insects and extending its whole 

 length, run two cylindrical tubes c , which communicate 

 with the spiracles d , and from which issue, at points op- 

 posite to those organs, other tubes which ramify ad in- 

 Jinitum, and are distributed to every part of the body 6 . 

 The first of these tubes are called the trachea and the 

 latter the bronchia. This structure appears, however, 

 not to be universal : it is to be found in caterpillars and 

 many Dipterous larvae ; but in that of the rhinoceros* 

 beetle and other Lamellicorns, the bronchia branch di- 

 rectly from the spiracle, the bottom or interior mouth 

 of which is lined by a membrane from which they pro- 

 ceed 6 : something similar has been observed to take 

 place in many insects in other states, as the common 

 cockchafer f ; in the pupa of Smerinthus Populi g ; in the 

 Cicada h ; in the Locust tribe 1 ; and many others. In 

 the Cossus, or larva of the great goat-moth, the trachea 

 commences with the first spiracle, and finishes a little 

 beyond the last, after which it diminishes considerably 

 in diameter, and terminates in several branches or bron- 

 chia, which proceed to the anal extremity of the body k . 

 The bronchia which originate from the trachea in the 



a Treviranus Ibid. 24. PLATE XXIX. FIG. 1. 



o PLATE XXI. FIG. 3. a b. c Ibid. a. 



d Ibid. b. e Sprengel Commcntar. t. \.f. 1. 



f Ibid.f. 10. g Ibid.t.\\.f. 15. 



h Malpigh. De Bombyc. t. iii./. 3. * Ibid. t. iv./. 1. 



k Lyonet Anat. 101. 



