THE STRUCTURE OF INSECTS. 7 



edge, adapted for biting. The mandibles are situated on 

 each side of the mouth-opening. Behind the mandibles 

 are the maxillae (Fig. 1), which are divided into three lobes, 

 the inner armed with teeth or spines, the middle lobe un- 

 armed and spatula-shaped, while the outer forms a five- 

 jointed feeler called the maxillary palpus. The maxillas are 

 accessory jaws, and probably serve to hold and arrange the 

 food to be ground by the true jaws. The floor of the mouth 

 is formed by the labium (Figs. 1 and 2), which in reality 

 is composed of the two second maxilla?, soldered together in 

 the middle, the two halves being drawn separately in Fig. 1. 



Within the mouth, and situated upon the labium, is the 

 tongue (lingua], which is a large, membranous, partly hol- 

 low expansion of the base of the labrum; it is somewhat 

 pyriform, slightly keeled above, and covered with fine, stiff 

 hairs, which, when magnified, are seen to be long, rough, 

 chitinous spines, with one or two slight points or tubercles 

 on the side. These stiff hairs probably serve to retain the 

 food in the mouth, and are, apparently, of the same struc- 

 ture as the teeth in the crop. The base of the tongue is 

 narrow, and extends back to near the pharynx (or entrance 

 to the gullet), there being on the floor of the mouth, behind 

 the tongue, two oblique slight ridges, covered with stiff, 

 golden hairs, like those on the tongue. 



The student may separate the body, after being hardened 

 in alcohol, into tlie parts represented by Fig. 1, as indicated 

 by the table on the following page, and neatly gum them in 

 their proper order upon a card with liquid glue or mucilage. 



Internal Anatomy. The internal anatomy may be studied 

 by removing the dorsal wall of the body, and also by harden- 

 ing the insect several days in alcohol and cutting it in two 

 longitudinally by a sharp scalpel. 



The cesophagus (Fig. 4, ce) is short and curved, contin- 

 uous with the roof of the mouth. There are several longi- 

 tudinal irregular folds on the inner surface. It terminates 

 in the centre of the head, directly under the brain or supra- 

 oasophageal ganglion, the end being indicated by several 



