INSECTA. 



We m-ust now examine more minutely the different portions of 

 which the alimentary canal may consist, premising at the same 

 time that the structures mentioned do not invariably exist together, 

 as sometimes one part, and sometimes another, may be entirely 

 wanting, or only found in a very rudimentary condition. They 

 are the Crop, the Gizzard, the Stomach, the Small Intestine, 

 and the Large Intestine. 



(302.) The Crop, or Sucking- Stomach, as it is called by some 

 writers, is only met with in Hymenoptera, Lepidoptera, and Di- 

 ptera, insects which have no gizzard.* In bees, wasps, and other 

 Hymenoptera, it is a simple bladder-like distension of the oesophagus 

 (Jig. 116, b) ; in butterflies and moths it forms a distinct bag, 

 that opens into the side of the Fig. 116. 



gullet (Jig. 117, v, v) ; while in 

 the Diptera it is a detached ve- 

 sicle, appended to the oesophagus 

 by the intervention of a long thin 

 duct. This organ, which in bees 

 is usually called the honey blad- 

 der, is regarded by Burmeister, 

 who founds the opinion upon the 

 result of experiments made by 

 Treviranus upon living insects, as 

 being not merely a receptacle for 

 food resembling the craw of birds, 

 as Ramdohr j- and Meckel con- 

 sider it, but as being a sucking instrument for imbibing liquids, 

 by becoming distended, as he expresses it, and thus, by the rare- 

 faction of the air contained within it, facilitating the rise of the 

 fluids in the proboscis and oesophagus. It must, however, be 

 confessed that there is something very anomalous in the idea of a 

 delicate bag having the power of distending itself ; its muscular 

 walls might indeed contract, but that a thin sacculus should forci- 

 bly expand itself would be a fact new to physiology. 



(303.) The Gizzard is found in insects which possess mandibles, 

 and live upon solid animal or vegetable substances. It is a small 

 round cavity with very strong muscular parietes, situated just above 

 the stomach properly so called, and, like the gizzard of granivorous 

 birds, is employed for the comminution of the food preparatory to 



* Burmeister, op. cit. p. 125. Treviranus, Vermischte Schriften. 



t Ramdohr, iiber die Verdauungswerkzeuge der Insecten. Halle, 1811. 



