58 



Make a drawing of the tracheal system, tracing the longi- 

 tudinal and lateral vessels as far as possible. 



Cut off a small piece of one of the lateral trachese and ex- 

 amine it in water or glycerine on a slide under the micro- 

 scope. Note the tubular character of the trachea, and note 

 the five transverse striations due to spiral thickenings of the 

 inner wall of the vessel. Pull apart pieces of trachea to show 

 the tcenidia. See p. 47. Make a drawing of a piece of 

 trachea to show its structure. 



For an account of the respiration of insects, see the Cam- 

 bridge Natural History, Vol. V., pp. 128-132. 



The reproductive organs. — The reproductive organs 

 consist in the male of two small, white oval bodies, the testes, 

 lying one on each side of the large intestine imbedded in the 

 muscles of the tenth body-segment, and of a delicate duct, 

 the vas deferens, running posteriorly from each to the ventral 

 wall of the penultimate segment. In female specimens the 

 white bodies, ovaries, are larger and more elongate than the 

 testes of the male, and the oinducts (corresponding to the vasa 

 deferentia) are more easily seen. 



Make a combined drawing showing the alimentary canal, 

 salivary glands, tracheal trunks, and reproductive organs in 

 position in the body. 



For a dissection of the reproductive organs in an adult 

 insect, see pp. 41-46. 



The nervous system. — Remove the alimentary canal, 

 cutting across the oesophagus near the anterior end of the pro- 

 ventriculus. The brain is composed of two main lobes united 

 posteriorly and lying above the oesophagus. Beneath the brain, 

 just under the oesophagus, lies the subxsophageal ganglion, 

 which is connected with the anterior end of the brain-lobes by 

 the circumoesophageal commissures, nerve-cords which together 

 with the brain and suboesophageal ganglion form a complete 

 ring around the oesophagus. Back of the suboesophageal 



