INTERNAL ANATOMY OF INSECTS. 131 



pathi, Chrysopa Pcrla, and lulus terrestris. The most 

 usual number of the saliva-secretors is two*; but some- 

 times, as in the first of the last-named insects, there is 

 only one b ; in others (Pcntatoma Baccarum) there are 

 three, the exterior one consisting of a pair of reservoirs 

 connecting with the gullet by a single capillary tube c ; in 

 Pentatoma prasina there appear to be four d ; in Nepa 

 cinerea, even six the exterior double pair in this insect, 

 under a powerful lens, is found to consist of spherical 

 vesicles, resembling somewhat a bunch of currants 6 ; and 

 in Syrphus arcuatus they are covered with four rows of 

 similar ones f . In the flea they consist of two pair of 

 spherical reservoirs, each of which is connected with a 

 short tube, which uniting with that of the other forms a 

 common capillary one connecting with the mouth or 

 gullet & ; these organs sometimes terminate below in 

 slender vessels; thus, in Nepa, the inner pair terminates 

 in a single vessel of this description h , and in Tabanus and 

 Hemerobius apparently in many '. It admits of a doubt 

 however, as was lately observed, whether in the Hemi- 

 ptera, which have usually more than a pair of these organs, 

 some are not rather food-reservoirs as in the Diptera. 



The saliva-secretors open either into the instruments 

 of suction themselves (Tabanus, Musca) ; or into the en- 

 trance of the gullet (Pentatoma, &c.) ; or, lastly, into that 

 of the stomach (Syrphus, Bombylius}. Those which lie at 

 the entrance of the stomach consist only of a blind uni- 



a Ramdohr Anal. t. xviii./. 1. M.f. 5. F. < Ibid. t. x./. 1. m. 



Ibid. t. xxii./. 3. ML. Ramdohr regards the double one as a 

 pair; but as they terminate in a single tube, they ought to be reckoned 

 as one. * Ibid.f. 4. e Ibid.f. 2. K, L, M, N. t. xxiii./ 6. 



f Ibid. 177. /. xxi./. 3. F. F. * flM t f t 2. G S H. 



h Ibid. t. xxii./. 2. L. ' l Ibid. t. xxi./. 1. O. t. xvii./. 6. n. 



K 2 



