INTERNAL ANATOMY OF AN INSECT 13 



knee-like form to the elongated head. The entire mass is highly 

 muscular, and may either be protruded, as in feeding, or quite 

 largely withdrawn, while at rest. Lying on top of the grooved 

 labium is the inconspicuous prolonged spade-like labrum, which 

 forms with the hypopharynx a sucking tube, supported by the 

 labium, which latter also encloses the salivary canal. By an 

 examination of the labrum it will be seen that it forms a kind of 

 convex cover to the concaved hypopharynx, thus giving rise to 

 a food tube. The maxillae have evidently become fused with 

 the fleshy knee of the proboscis, and only the prominent max- 

 illary palpi remain. 

 Draw and label parts. 



EXERCISE 4 



INTERNAL ANATOMY OF AN INSECT 



It is important that the student familiarize himself with the 

 internal anatomy of an insect, with special reference to the di- 

 gestive system and its accessory structures, such as the salivary 

 glands. For this purpose a grasshopper is to be dissected, ow- 

 ing to ease of manipulation. If the student has time it is recom- 

 mended that the internal anatomy of a stablefly be studied for 

 the sake of comparison. 



With fine pointed needles or scissors open the dorsal abdominal 

 wall, separating the right and left sides to expose the intestine. 

 Small pins will be found convenient to pin down the parts and 

 thus allow more freedom in working. The insect should be 

 dissected under water in a dish with a paraffin floor. 



A. Determine the following parts, drawing and labelling the 

 same. 



a. The mouthparts, without reference at this time to details; 

 these have already been studied. 



b. The oesophagus, a straight tube leading from the pharynx 

 to the crop. 



