ORGANS OF REPRODUCTION. 85 



When an egg is laid by an insect, it is, except in 

 a very few cases, glued to the place where it is laid 

 by a sticky fluid provided for that purpose, and dis- 

 charged along with the egg, or immediately after it ; 

 the vessel producing which fluid in the louse may 

 be seen in the figure. The louse glues its eggs to hairs"; 

 moths and butterflies glue theirs on the bark or leaves 

 of plants and trees, where they usually remain 

 through the winter, to be hatched the following 

 spring. 



It is thence obvious that the eggs of insects, thus 

 firmly glued, cannot, as has been fancied by the un- 

 learned, as well as by philosophers, float about in the 

 air, than which, indeed, they are always much heavier. 



Several species of insects, instead of gluing their 

 eggs in this manner, place them in nests, as is done 

 by the bees and wasps, appropriately called miners, 

 masons, carpenters, or upholsterers, according to 

 the processes they pursue in building their nests. 



Other species dig holes in the ground, or cut out 

 grooves in wood, in which to lay their eggs, and are 

 provided with curiously-constructed instruments for 

 that purpose, such as the grasshopper, whose digging 

 instrument is like a scymitar; the saw-flies, whose 

 instrument is like a double saw ; and the gall-flies, 

 whose instrument is like an awl. 



Instruments for depositing eggs ; a, that of a cuckoo fly ; 

 b, that of a grasshopper } c, that of a saw fly. 



