62 GENERAL SCIENCE 



measures for their extermination have followed. Rats may 

 become infected by bites of fleas that have bitten plague- 

 stricken patients. Wherever these rats go the disease germs 

 may in turn be transmitted from the rats to persons by 

 agency of fleas. 



In these days of cement construction there is no excuse 

 for rat-haunted dwellings and storehouses. Hunting and 

 destroying rats on an extensive scale is expensive. Their 

 extermination can be accomplished in time by imposing 

 appropriate penalties for harboring rats upon owners of 

 ships and buildings. It should be kept in mind that rats 

 and mice remain only where food is available for them, and 

 that to properly protect foodstuffs at house, barn, store, 

 and warehouse from depredations of rats is to lessen their 

 numbers if not entirely to be rid of them. 



SUMMARY 



In agriculture the destruction wrought by insects, especially while 

 in the larva or "worm" stage, is almost incalculable. Insects are not 

 only a pest so far as man's comfort goes, but they are a menace to his 

 health and to life itself. 



Insects constitute the most numerous division of the animal kingdom. 

 Between the egg when hatched, and the fully developed insect that 

 in turn lays eggs for another generation, there are variations in the 

 length of time required by different species to complete the "cycle." 

 There are differences in the succession of changes that occur. How- 

 ever, from the eggs come the larvae variously known as "worms," "mag- 

 gots/* "grubs," or "caterpillars;" then comes the pupa or "chrysalis" 

 stage, followed by that of the grown insect. 



Insects in general are characterized by having the three parts head, 

 thorax, and abdomen. The eyes and antennae are parts of the head; 

 to the thorax are attached the legs and wings; and the abdomen is 

 made up of connected ring-like parts. 



While there are many kinds of flies, some of which are tormenters 

 of both men and animals, the common house fly as a carrier of filth and 

 disease germs should be exterminated as a sanitary measure. 



The discovery of the part played by some kinds of mosquitoes in the 



