428 THE INSECTA. <^ 339. 



plan. It exceeds more or less the length of the body, and there is a crop 

 at the posterior extremity of the (esophagus upon which succeeds a long 

 and tortuous stomach. Upon the cardiac portion of this last there are 

 inserted two to four caeca directed either forwards or backwards, and with 

 some larvae of the Muscidae, there is also a long, sucking stomach upon 

 one of the sides of the oesophagus. '■'''^' 



With the larvae of the Neuroptera, which suck up their liquid food through 

 tubular mandibles, the posterior extremity of the oesophagus is dilated into 

 a pyriforni sucking stomach, which is followed by the proper stomach, 

 large, of median length, and slightly flexuous. The extremely small ileum 

 is long and makes several convolutions, while the colon is large, vesiculi- 

 form, and continuous into a horny tubular rectum. <'^*^ 



§ 339. 



As to the grandular appendages of the digestive canal of the Insecta, 

 the Salivary Organs are quite widely distributed, as well with the Imagines 

 as with the Larvae and feeding Pupae. Tliese organs consist of one, or 

 two, rarely three pairs of colorless tubes of unequal length. These are 

 sometimes prolonged into the thorax, while in other cases they accompany 

 the digestive canal into the abdominal cavity where it makes many convo- 

 lutions. Their excretory ducts are composed of a solid membrane, and are 

 distinctly separated from the glandular portion.'^' This last is composed 

 of three layers, namely : an external, homogeneous envelope, — an intimate 

 tunic accompanying the excretory duct, — and a middle layer composed of 

 colorless, glandular, nucleated cells, which often form very fine excretory 

 tubes opening into the common duct. Frequently, also, these ducts contain 

 a spiral filament like the tracheae ; they open, each, at the base of the oral 

 cavity by a distinct orifice, and it is rare '-' that they unite, forming a 

 common duct; sometimes they have, near their excretory openings, special 

 salivary reservoirs.'"' With very many Aptera,'''* Diptera, Lepidoptera, 

 and Coleoptera,''^' the salivary organs consist of two simple tubes, which, 

 with the larvae of the second and third of these orders, often extend a con- 

 siderable way into the abdominal cavity."'" With the Cerambycidae, Te- 



37 See Swammerdamm, Bib. der Nat. Taf. XLI. 1 For the intimate structure of these organs, see 

 fig. 6, Tab. XLIII. fig. 5 {Stratiomys and Pio- H. Meckel, iu Midler's Arch. 1846, p. 25, Taf. I. 

 phila); Rmndohr, loc. cit. Taf. XIX. fig. 1 II. 



(Musca) ; L. Dufour, Ann. d. Sc. Nat. XI. 1839, 2 Piophila, Musca, Sarcophaga, Tabaniis, 



\>. 212, PI. V. fig. 23, XII. p. 13, 18, PI. I. fig. 1, Hippobosca, Oestrus, Mordella^ Mantis, and 



4, and I. 1844, p. 372, PI. XVI. fig. 8 (Ceroplatus, Forficula. 



Sapromyza, Piophila). 3'with Forficula, Musca, Sarcophaga, and 



The metamorijliosis of this digestive canal, in Hippobosca, each of these excretory ducts is dilated 



tlie pupa of Sarcophaga carnaria, is represented into a roundish rcservoii' ; but with the Tennitidae, 



in a suite of ligures publislied by Suckow, in Acrididae, Achetidae, and Mantidae, there is an 



Heusinger's Zeitsch. III. Taf. IX. fig. 147-153. oblong, pedunculated reservoir common to both 



But Suckow has fallen into the same error as ducts. See, for the figures, the various memoirs of 



Ramdohr (loc. cit. p. 171) in regarding the caecal L. Diifour. 



appendages of the stomach of the larvae as four 4 With the Nirmidae. 



tubes connecting the stomach with the salivary J Pyrochroa, Lixus, Phyllobius, Diaperis, 



canals. Lema, Oedemera, Chrysomela, Coccinella. In 



38 See Ramdohr, loc. cit. p. 154, Taf. XVII. fig. this last genus, the two salivary vessels are to- 

 1 ; and L. Dufour, Recherch. &c. p. 689, PI. XII. rose. 



fig. 175 (Myrmeleon). The large intestine together 6 See the figures in the works of Swammerdamm, 



with the rectum, does not serve, with this larva, as Lyonei, Ramdohr, Suckow, Herold, and L. Du- 



a defecating organ, but, as is very extraordinary, four, 

 has the function of a Spinneret (see § 347). 



