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ZOOLOGY 



Firefly. — One form not usually considered by boys and girls 

 as a beetle is the firefly. The light produced by this beetle is 

 believed by scientists to be caused by a true oxidation of fatty 

 substances stored in the cells of the lower surface of the abdomen. 

 Beetles Useful to Man. — Several beetles are of value to man. 

 Most important of these is the natural enemy of the orange-tree 



scale, the ladybug, or ladybird beetle. This 

 insect preys upon the scale insect. In New 

 York state it may often be found feeding 

 upon plant lice or aphids which live on rose 

 bushes. The carrion beetles and many„water 

 beetles act as scavengers. The sexton beetles 

 bury dead carcasses of animals. These beetles 

 are provided with antennae that have the end 

 segments peculiarly modified for the purpose 

 of smelling. 



Sexual Dimorphism. — Among beetles, as among 

 other insects, the two sexes sometimes show marked 

 differences. This is particularly well shown in the 

 case of the stag beetle, shown in the illustration. 

 This difference in form between male and female of 

 a given species is known as sexual dimorphism. 



Hemiptera 



Bugs. — The cicada, or as it is incorrectly 

 called, the locust, is a familiar insect to all. 

 Its droning song is one of the accompani- 

 ments of a hot day. The song of the cicada 

 is produced by a drumlike organ which 

 can be found just behind the last pair of 



legs. The sound is caused by a rapid vibration of the tightly 



stretched drumhead. 



Characteristics of the Cicada. — In a living animal notice that the body 

 is heavy and bulky. The wings, four in number, are relatively small, but 

 the powerful muscles give them very rapid movement. The anterior wings 

 are larger than the posterior. The legs are not large or strong ; the move- 

 ment when crawling being sluggish. Note the color of the body; evidently 

 the insect depends upon protection by means of assuming the colors of the 



The stag beetle, showing 

 sexual dimorphism. 

 Male above, female 

 below. Natural size. 



