12 PHYLUM ARTHROPOD A 



The Reproductive System : the Female Organs. The two ovaries 



are closely bound together by a web of connective tissue and 

 tracheae so as to form a single mass, which Hes above the intestine. 

 If your specimen is a female, part this mass along the median line 

 and with a needle gently remove some of the connective tissue 

 surrounding it. Examine it with a hand lens ; each side is a sepa- 

 rate ovary and will be seen to be a collection of parallel, tapering 

 tubules, their smaller ends being in the median line, their longer 

 ends projecting back to the tubelike oviduct. These tubules are 

 called ovarioles ; it is in them that the eggs develop. How many 

 tubules do you count on each side ? Notice the elongated eggs in 

 each ovariole. How many do you see in each one ? The two ovi- 

 ducts proceed from the ovaries to the ventral side of the animal, 

 where they unite to form a median tube, the vagina, which opens 

 to the outside between the ovipositors. Just above the vagina is 

 a small sac, the receptaculum seminis, which is connected by a 

 long, sinuous duct with the exterior. The sac becomes filled 

 with spermatozoa during pairing, which fertilize the eggs as they 

 pass out of the vagina. 



The Male Organs. The paired testes which secrete the sperma- 

 tozoa lie above the intestine, bound together by connective tissue 

 and fat. Each testis consists of a bundle of elongated tubes, with 

 which a duct called the sperm duct connects posteriorly. The 

 two sperm ducts run, one on each side of the intestine, to the 

 ventral side of the animal, where they meet to form a median 

 tube, which leads to the genital pore just beneath the anus. 



Exercise 13. Make a semidiagrammatic drawing representing all the 

 parts of the reproductive tract of your specimen. 



The Respiratory System. The spiracles have already been 

 noted. They are the external openings of the tracheae, a system of 

 fine air tubes which extend throughout the entire body of the 

 insect and through which fresh air is introduced into every part 

 of it. The blood is thus constantly aerated, and there is never 

 any venous blood present. This arrangement results in a very 

 active metabolism and is one of the causes of the extraordinary 

 amount of energy which characterizes most insects. With the 



