ARTHROPODA. 267 



and the degree of differentiation. Find the openings 

 to the air-sacs on the ventral surface of the abdomen. 

 Locate the spinning glands. Number? 

 Activities and Habits. How do the legs act in walking? 

 At what joints are they flexed at various parts of the step? 

 Do all the legs on one side act in unison? Observe the spin- 

 ning action. Does the spider ever produce the threads except 

 when weaving a web? Describe. Determine if possible the 

 kind of web formed by the species studied. Or find as many 

 types of nest or web as possible and learn to recognize the 

 spiders producing them. How does the spider travel on its 

 web ? Where do spiders place their webs ? Place a fly or other 

 insect in a newly constructed web and record the actions of 

 the spider. Can you devise means to prove whether the spider 

 possesses the sense of smell? 



303. The Grasshopper. Several species of the locusts 

 may be found in almost every locality. They are especially 

 abundant in the early autumn. For laboratory study select 

 the largest species found in sufficient abundance. In connec- 

 tion with the securing of material the students should make 

 observations on the following points: 



1. Habits. Where and under what circumstances found? 

 At what time of the year does this species occur in greatest 

 abundance ? Under what circumstances are they most active ? 



2. Methods of Locomotion. How many methods seem 

 available? Degree of efficiency of each ? Under what circum- 

 stances is each used? What distance can be attained at one 

 effort? Continue the study later in more limited quarters, as 

 in the room and under a bell-glass. Compare the work of 

 the various legs. Are the wings used at all in jumping? 



3. Protective Features. Coloring; to what extent do you 

 find this of protective value ? Reasons. Does the animal show 

 a distinct instinct for hiding? Compare all available species 

 in these regards. 



4. Do they produce definite sounds? Under what circum- 



