130 ANATOMY. 



constrictions. Generally, upon both upper and under surface, a narrow 

 sinewy or muscular stripe runs longitudinally, for the purpose of 

 strengthening the there more delicate envelope. Meckel informs us * 

 that this stomach in Acheronlia Atropos is shaggy externally, a solitary 

 instance of this structure in the Lepidoptera. 



The longitudinal, more tubular, and regularly transversely folded 

 stomach of the Hymenoptera (PI. XVII. f. 10. D) approaches very closely 

 in structure to that of the Lepidoptera. It commences with a funnel- 

 shaped orifice, which is evidently analogous to the before-described 

 proventriculus, and as such projects into the cavity of the sucking 

 stomach, which can be closed by valves that open inwardly f- This 

 funnel-shaped orifice facilitates the passage of the food from the oeso- 

 phagus into the stomach, its aperture being thereby brought nearer to 

 the former, indeed, during suction, rising quite up to it ; the valves 

 however preventing the return of the chyme into the sucking stomach. 

 This structure of the stomach is found in all the Hymenoptera, but it 

 varies much in compass ; in some (Sirex) it is short, broad, and straight, 

 the crop, on the contrary, is very long and nodose ; in others (Chrysis) 

 it is distended in the middle and recurvate at the extremity ; in the 

 bees and wasps it is of tolerably equal breadth, but not straight, for it 

 bends inwardly at both ends, so that it is partially inclined towards the 

 axis of the body. 



In the larvae of these insects the whole intestinal canal (PI. XVII. 

 f. 9. D) consists but of this transversely folded stomach, and all the fol- 

 lowing divisions, including also the anus, are deficient : this stomach, 

 consequently, is more compactly constructed in them than in any other 

 insect, it being composed of five skins, whereas the others have but 

 three. It is probable that both the mucous and muscular membranes 

 have separated into two layers J. 



In the Diptera (PI. XVIII. f. 3. D) the stomach is a long tube, which 

 frequently distends at the two extremities, and is narrowest in the 

 centre (Musca); a callous ring is found at the cardia, which is the 

 remains of a small bladder existing there in the larva state ; the vicinity 

 of the cardia is granulated, that is, uneven, arising from transverse and 

 longitudinal striae. Some of the large group (perhaps all), which 

 Latreille calls the Diptera Alhericera, have peculiar, glandular, 



* Verglci. Anatomie, vol. iv. p. 87. 



f Compare Treviranus, Vermischte Schriftcn, vol. ii. PL XV. f. 2. 



J Compare Suckow,in Heusinger Zcitschr. f. (1. Org. Phys. vol. iii. p. 18. PI. VI. f. 131. 



