INTERNAL ANATOMY OF THE LOCUST. 261 



middle lobe unarmed and spatula-shaped, while the outer forms a five- 

 jointed feeler called the maxlUary imlpus. The maxillee 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. 12 

 and 13), which in reality is composed of two second maxillae, soldered 

 together in the middle, the two halves being drawn separately in 

 Fig 12. 



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

 (lingua)^ which, as observed in (7. femur-rubrum, is a large, membran- 

 ous, partly hollow expansion of the base of the labrum ; it is some- 

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

 which, under a one-fifth lens, 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, appa- 

 rently, of the same structure as the teeth in the proventriculus. 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. 



INTERNAL ANATOMY. 



The cesopliagus (Fig. 14, ce) is short and curved, continuous with the roof 

 of the mouth. There are several longitudinal irregular folds on the 

 inner surface. It terminates in the center of the head, directly under 

 the supra-cesophageal ganglia, the end being indicated by several small 

 conical valves closing the passage, thus preventing the regurgitation of 

 the food. 



The oesophagus is succeeded by the crop {ingluvies). It dilates rapidly 

 in the head, and again enlarges before passing out of the head, and at 

 the point of first expansion or enlargement there begins a circular or 

 oblique series of folds, armed with a single or two alternating rows of 

 simple spine-like teeth. Just after the crop leaves the head the rugae 

 or folds become longitudinal, the teeth arranged in rows, each row 

 formed of groups of from three to six teeth, which point backwards so 

 as to push the food into the stomach. In alcoholic specimens the folds 

 of the crop and oesophagus are deep blood-red, while the muscular por- 

 tion is flesh-colored. It is in the crop that the ^' molasses" thrown out 

 by the locust originates, as we have found the fluid in opening the crop 

 of living specimens, and it consists of partially digested food. The crop 

 terminates a little behind the insertion of the middle pair of legs. 



The proventriculus is very small in the locust, easily overlooked in 

 dissection, while in the green grasshoppers it is large and armed with 

 sharp teeth. It forms a neck or constriction between the crop and true 

 stomach. It may be studied by laying the alimentary canal open with 

 a pair of fine scissors, and is then seen to be armed with six flat folds, 

 suddenly terminating posteriorly, where the true stomach (chyle-stomach. 



