SCfflSTOCERCA AMERICANA Drury 



Material. Schistocerca americana or the common Amer- 

 ican locust is the largest grasshopper of the United States and 

 for that reason well adapted for dissection. Unfortunately the 

 dissection of the insect comes always at the wrong time of year 

 when live specimens are not available. It should not be dis- 

 sected at the beginning of the course, not only because of the 

 complexity of the organization, but also and chiefly because of 

 the impossibility of understanding its bearing upon the problem 

 of segmentation without some knowledge of other related forms. 

 The specimens should be preserved in 70% alcohol and soaked 

 in water for twenty-four hours before dissection. Every student 

 should receive two preserved specimens, one of which must be a 

 male, the other a female, two fresh specimens if available at the 

 time, and, if possible, prepared slides with sections through the 

 chordotonal organ, antennae, compound eyes, and various in- 

 ternal organs. 



Descriptive Part 



Schistocerca americana, or American locust, is a typical repre- 

 sentative of the Order Orthoptera, Class Hexapoda or Insects. 

 In its structure it is much more primitive and generalized than 

 many other insects and shows well the metamerism of the body. 



Segmentation. The body of the locust is, in all probabil- 

 ity, composed of twenty-one somites. The first six somites are 

 fused permanently together. They form the head. The next 

 three somites form the thorax. The abdomen shows only eleven 

 segments, but the eleventh segment is probably composed of 

 two somites. 



Head and appendages. Three of the six somites of which 

 the head is composed are preoral in position. The first is the 



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