418 ESSENTIALS OF ZOOLOGY 



of the body, parts of the segments may be lost. Regardless of the 

 amount of variation in this respect, we lind that the segments are 

 always grouped into three regions, Imown as the head, thorax, and 

 abdomen. 



The head is made up of a number of segments, which are fused 

 together, forming a boxlike structure known as the epicranium. This 

 boxlike piece which surrounds the eyes and forms the basis of 

 attachment for the movable parts of the head extends down the 

 front of the head, between the eyes, to the transverse suture, and 

 down the sides of the head to the base of the mouth parts. The 

 sides of the epicranium below the compound eyes are known as 

 the genae, or cheeks, Avhile the front of the head between the eyes is 

 called the frons. 



The grasshopper has both compound and simple eyes. The com- 

 pound eyes are situated upon the upper portion of the sides of the 

 head, and are large, oval areas with smooth, highly polished sur- 

 faces. If the eye is examined wdth a dissecting microscope, the 

 surface will be seen to be made up of a number of hexagonal areas, 

 which are known as facets. The simple eyes or ocelli consist of three 

 small, almost transparent, oval areas. One of the ocelli is situated on 

 the front of the head, just below the margin of the impression which 

 contains the bases of the antennae, and in contact with the upper 

 portion of the compound eye. 



The antennae or feelers are two threadlike processes situated 

 median to the compound eyes. Each consists of about twenty-six 

 segments. On the front of the head there is a short rectangular 

 piece, called the clypeus, which is attached by its upper edge to the 

 epicranium, and on the lower edge to the labrum. 



The mouth parts consist of a number of separate parts attached 

 to the ventral region of the epicranium. The first noticeable part 

 is the lahrum, or upper lip, a flaplike piece attached to the lower 

 edge of the clypeus. The free edge is deeply notched on the median 

 line. Just beneath the labrum are the mandibles, or first pair of 

 jaws. Each mandible consists of a single piece which is notched 

 on the inner grinding surface to form a number of ridges or teeth. 

 A second pair of jaws, the maxillae, may be exposed by the removal 

 of the mandibles. Each maxilla is composed of a number of parts, 

 consisting of the cardo or proximal hinge part of the structure; the 

 stipes, the lacinia, a sclerite which bears some teeth on its terminal 



