184 ARTHROPODA. 



4. Compare the organs of the head with those of the preced- 

 ing form. 



Make a drawing of the under side of one segment. 



Williams: Habits and Structure of Scutigerella immaculata. Proc. Bost. 

 Soc. Nat. Hist., 33, 1907. 



INSECT A. 



ACRIDIUM. (Grasshopper.) 



Study grasshoppers as they occur in nature and determine 

 as far as possible the following points: 



1. Do they see or hear? Are they equally sensitive to touch 

 on all parts of the body? Are these animals well provided with 

 sense organs? 



2. What is their food? Are all plants eaten or are some 

 avoided? See how the mouth parts are used in feeding. 



3. What are the important enemies of grasshoppers? How 

 do they escape their enemies? Do they hide? Are they pro- 

 tectively colored? How does jumping serve them better than 

 crawling? How many times its length can a grasshopper 

 jump? 



4. During late summer and autumn you may find individuals 

 depositing eggs. See if you can determine how the end of the 

 body is worked into the ground. 



For study it is desirable to use a rather large, freshly killed 

 or alcoholic specimen. 



The body is divided into three well-marked regions. 



1. The Head. — Is it movable? Does it need to be as mova- 

 ble as your own head ? It bears several organs. 



(a) The compound eyes. Examine one with a lens or remove 

 its outer covering and examine it with a compound microscope. 

 You should understand the structure of the whole eye and how 

 it gives a single visual image. 



(b) The ocelli, three in number, one near the middle of the 

 front part of the head and the others placed near the bases of 

 the antennae. 



