16 THE GRASSHOPPER 



LABORATORY STUDY 



Work out the divisions of the body of the grasshopper : head, thorax, 

 and abdomen; the position of eyes. How are the antennae related to 

 the eyes ? How many distinct mouth parts are there ? The teeth or 

 jaws are the most useful in getting food. How do the jaws work ? 

 Sketch the head to show these parts with the mouth open. 



Notice the attachment of the head to the thorax. The head fits into 

 the thorax. The loose anterior (front) portion of the thorax is the pro- 

 thorax (forward thorax). The first pair of legs is attached to it. Sketch 

 the prothorax to show it and its legs. The portion of the thorax back of 

 the prothorax is divided into two regions: the mesothorax (middle 

 thorax) and the metathorax (back thorax). The line between them is 

 not clear. Sketch these parts together with the legs and the wings. The 

 jumping legs are attached to the metathorax ; the outer wings to the 

 mesothorax ; the inner wings to the metathorax. The inner wings are 

 used in flying. The leg of the grasshopper consists of : (1) a small 

 section close to the body (the coxa) ; a long muscular part free from 

 spines (femur) ; a slender spiny part (tibia) ; and the three segments of 

 the foot (tarsus) . The last segment of the foot is furnished with hooks 

 which help the grasshopper in climbing, while the spines on the tibia pre- 

 vent slipping as the grasshopper jumps. The large muscles in the femur 

 of the last pair of legs, the spines on the tibia, and the hooks on the tarsus, 

 are special adaptations which help the grasshopper in various ways. 



Notice the tapering abdomen, composed of ten segments (rings) or 

 parts of segments. Notice the depression and membrane in the first 

 segment. This is the auditory organ, but it is not a true ear. Sketch 

 the abdomen to show its features. The spiracles are located on the sides 

 of the abdomen. 



8. Metamorphosis. — All animals which pass through a 

 marked change in external appearance as they become full 

 grown are said to undergo a metamorphosis (met-a-m6V- 

 fo-sis : Greek, meta, change; morphe, form). These 

 changes are more marked in such insects as the ants and 

 bees than in the grasshopper. For this reason we speak 

 of two forms of metamorphosis — complete and incomplete. 



9. Incomplete Metamorphosis. — The newly hatched grass- 

 hopper, while very small, looks enough like a wingless 

 grasshopper to be identified as belonging to the grass- 



