132 INTERNAL ANATOMY OF INSECTS. 



form tube a ; but there is commonly to be distinguished in 

 those that open into the mouth, a reservoir, varying in 

 shape in different species, and terminating in a capillary 

 tube, or tubes, at one or both extremities b . In Bugs, 

 two pair of these vessels are often present, one of which 

 opens into the stomach (Reduvius), or gullet (Pentatoma\ 

 but the other into the instruments of suction c . In the 

 Diptera they open into the stomach when the insect feeds 

 only upon the nectar of flowers (Syrphus), and into the 

 proboscis when it feeds upon both animal and vegetable 

 juices (Tabanus, Musea). The function of the fluid se- 

 creted by these organs is to moisten or dilute the food 

 before it is received by the instruments of suction and 

 passed to the stomach d . When a common house-fly ap- 

 plies its proboscis to a piece of sugar, it is easy to see 

 that it moistens and dissolves it by some fluid. 



iii. Varnish-seer etor (Colleterium). In butterflies, 

 moths, and several other insects, one or more vessels 

 called blind vessels open into the oviduct, concerning 

 the use of which, physiologists are not agreed. In the 

 cabbage butterfly there is a pair of ovate ones, or rather 

 a bilobed one, each lobe of which externally terminates 

 in long perplexed convolutions, not easily traced, filled 

 with a vellow fluid, which Reaumur and Herold think 

 is used for varnishing or gumming the eggs, so that they 

 may adhere to the leaves on which they are deposited : 

 it may probably serve likewise for other uses 6 . Another 

 vessel is also to be found in the above butterfly, which en- 



a Ramdohr Anat. f. xx./. 6. D. 



" Ibid. t. xxii./. 1. K, L.f. 2. /, K, L. 



c Ibid.f. 3, 4, 5. d Ibid. 57. e Reaum. ii. 81. He- 



rold Expl. of Plates, x. Malpigb. De Sombyc. 37. PLATE XXX. 

 FIG. 12. c. 



