330 General Biology 



mally found in any animal, are also 

 found in them, though these may vary 

 considerably as to shape and size. For 

 example, those insects, which feed on 

 vegetation, have longer digestive tracts 

 than do those feeding on animal 

 matter. 



The parts of the digestive system 

 (Fig. 214, E) are: The mouth or 

 buccal cavity; a slender oesophagus, 

 dilated to form a thin-walled crop; a 

 muscular gizzard or proventriculus ; a 

 glandular stomach, or ventriculus, 

 from which little pouches, or caeca, 

 branch out ; and a long slender intes- 

 tine. At the junction of the stomach 

 and intestine, the slender Malpighian 

 tubules discharge their excretions into 

 the alimentary canal. 



As distinguished from the higher 

 forms of life no air-breathing insects 

 have lungs. They receive their oxygen 

 through a network of tubes, called 

 tracheae, which open through little 

 spiracles ( ) along 



the sides of abdomen and thorax (Fig. 

 215). 



If, therefore, one wished to chloro- 

 form or drown an insect, it could not 



be done by covering the head or placing the head under water. The 



abdomen and thorax would have to be covered with the anaesthetic or 



the water. 



ThrsalJoinl 

 white banded 



_ Based, band 

 fiasal end of segment 

 Apical end <f segment 



S tk tarsaljood- 



Fig. 213. 



I. External anatomy of Caloptenus and spretus, the head and thorax disjointed; 

 up, Uropatagium; f, furcula; c, cercus. (Drawn by J. S. Kingsley.) 



II. An adult mosquito much enlarged, with all the parts that are used in classi- 

 fication named. (Smith, N. J. Experiment Station, Bulletin 171, 1904.) 



III. Side view of Locust with the Thorax separate from the head and abdomen 

 divided into three segments. (I, III, from Packard's "Zoology," by permission of 

 Henry Holt & Co.) 



