INTERNAL ANATOMY OF INSECTS. 125 
usual number of the saliva-secretors is 7wo?; but some- 
times, as in the first of the last-named insects, there is 
only one>; in others (Pentatoma Baccarum) there are 
three, the exterior one consisting of a pair of reservoirs 
connecting with the gullet by a single capillary tube‘; in 
Pentatoma prasina there appear to be four’; in Nepa 
cinerea, even sizx—the exterior double pair in this insect, 
under a powerful lens, is found to consist of spherical 
vesicles, resembling somewhat a bunch of currants*; and 
in Syrphus arcuatus they are covered with four rows of 
similar ones‘. 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", and in Tabanus and 
Hemerobius apparently in many’. It admits of a doubt 
however, as was lately observed, whether in the Hemz- 
ptera, which haveusually more than a pazr of these organs, 
some are not rather, food-reservoirs as in the Diptera. 
The saliva-secretors open either into the znstruments 
of suction themselves (Tabanus, Musca); or into the en- 
trance of the gzlet (Pentatoma, &c.); or, lastly, into that 
of the stomach (Syrphus, Bombylius). "Those which lie at 
the entrance of the stomach consist only ef a blind uni- 
form tube*; but there is commonly to be distinguished in 
@ Ramdohr Anat. t. xviii. fil. AL fo. B. DUO tar Spek s Ti 
© Ibid. t. xxii. f. 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. d Ibid. f. 4 Tad. acails L, M, N. t. xxii. f. 6. 
« Ibid. Wdetaxst.7. 3. FP. & Thid. (2 2. G, U, 
By (rio Berghe @ aaa cree Oe bid te moc ul sO ne. Salah. Oo atc 
e Tbid, t. Xx. f. 6. D.- 
