THE INSECT S— ARTHROPODS 225 



of the females to attract the males. The moths are insects that are active 

 at night and the males might have a hard time finding their mates were 

 it not for a special gland which the females protrude from their bodies 

 when they are ready to mate. This gland has a characteristic scent and 

 a male quite some distance away becomes very excited when he smells it 

 and flies in the direction from which the odor is coming until he finds 

 the female. The antennae seem to be the olfactory organs and are much 

 more extensively branched in the male than the female moth. Some 

 day-flying insects, such as the flies, use sight to find their mates and can 

 usually be recognized by their large well-developed eyes. There is one 

 night-flying insect that also uses sight, the firefly. Fireflies carry their 

 own lanterns with them and give off the flashes of light in order to locate 

 each other in the dark. Many of the sounds made by insects as de- 

 scribed under insect voices are made by the males to attract the females. 

 In most cases only the males have the sound apparatus and it serves 

 solely for sexual attraction. 



The mating act usually consists of direct copulation with the male in- 

 seminating the female, usually only once during her lifetime. Seminal 

 receptacles are frequently present to store the sperms in the female's body 

 to fertilize the eggs as they are laid, sometimes as long as three or four 

 years after insemination, as in the queen bee. The method is slightly 

 different in the dragonflies. Before mating the male loops his abdomen 

 forward and discharges sperms into a little pouch on the second abdominal 

 segment. Then a female joins him in a flight grasping his abdomen with 

 her legs so that they are flying in a tandem fashion with the female be- 

 hind. During the flight the female will extend her abdomen forward 

 and insert it in the pouch on the male to obtain the sperms which he has 

 placed there. 



Reproduction seems to be the main purpose in life for adult insects 

 and they usually die shortly after they have fulfilled their reproductive 

 duties. In the male this is frequently soon after copulation ; in the female 

 after egg laying. In other insects, the adults are needed to give care to 

 the young and live to accomplish this important part of reproduction. 



Classification and derivation of words given at the close of Chapter 

 17. 



REVIEW QUESTIONS 



1. List the insect characteristics. 



2. What are the advantages and disadvantages of the insect method of res- 

 piration ? 



3. Distinguish between the three types of insect metamorphosis and give an 

 example of each type. 



