THE INSECTS. 125 



part becomes food for the young larvae, the re- 

 mainder she eats to sustain her in her extra- 

 ordinary work. At this stage she is the nurse of 

 the young community and gets nothing from out- 

 side. Soon, however, the young ants come to her 

 assistance, the fungus spreads, the real workers go 

 out to ravage the forest for leaves, the home is 

 enlarged, and very shortly the fungus beds are 

 extensive enough to support the whole com- 

 munity. Then the mother retires to her cell, and 

 goes on with her egg-laying, her children doing 

 everything else and feeding her and her young on 

 the fungus alone. 



South America is the home of a number of 

 insects that are very troublesome in some places. 

 Mosquitoes, sand-flies, pium-flies, a tiny bee that 

 sucks the eyelids, a fly which deposits its eggs 

 under the skin of man as well as animals, ticks and 

 the jigger-flea, all find out that we are not immune 

 against their attacks. In our absence they still 

 live, but no doubt they have discovered us. They 

 have one drawback, however, which tends to our 

 safety ; their eyes are microscopic. Few appre- 

 ciate the advantages of long and short foci 

 although all know something of the use of lenses. 

 We might hastily conclude that microscopic 

 lenses with short foci would be useful to us, 



