296 OUR HOUSEHOLD INSECTS 



body of the living or freshly killed bug is usually suffi- 

 ciently transparent for some of the chief branches to be 

 traced from the outside. 



The photographs in Plate VII. show the correspond- 

 ing organs of a water-beetle and a silkworm, and will 

 serve to indicate, more clearly than any verbal descrip- 

 tion can do, the sort of thing that is to be looked for in 

 a dissection. 



The structural details cannot be properly made out 

 till the tubes are removed from the surrounding organs, 

 and freed from the air they contain. The fine thread 

 which projects round their inner walls prevents collapse ; 

 and so well does it perform its function that even in the 

 dead and dried bodies of bugs, however ancient, such as 

 may sometimes be found in swarms behind panels and 

 wainscoting in badly infested houses, the tracheae can 

 still be recognised as perfect tubes after all the rest of 

 the soft parts have dried up and disappeared. All that 

 it is necessary to do with the dried carcase is to soak it 

 in water till it becomes sufficiently flexible to be mani- 

 pulated without breaking. On cutting through the skin, 

 the tracheal tubes will be found spreading about in 

 various directions, and may be examined where they 

 lie, or removed and placed between glass, when a high 

 power may be brought to bear upon them. There is no 

 object in insect anatomy that is more easily identifiable 

 than these breathing tubes, or more easily demonstrable, 

 and hardly any that forms a more beautiful and attrac- 

 tive subject of study or exhibition. 



Bugs are extremely prolific, and according to Southall, 

 who kept many for observation, sometimes produce eggs 

 as frequently as four times during the course of the 

 summer, whence their remarkably rapid multiplication 

 can be readily understood. The small size of the eggs, 



