52 ANIMALS OF LAND AND SEA 



are victimized mainly by the cuckoo-bees. The solitary bees, 

 the various burrowing types, the carpenters, carders, uphol- 

 sterers, varnishers, etc., form lines of cells each of which is filled 

 with food, provided with an egg, and sealed. The oil beetles 

 and the burglar bees each have found a way of dispossessing 

 the maker of these cells and of appropriating the food for their 

 own young. The httle stingless bees within the tropics, which 

 have the sting so small and blunt as to be useless though 

 their jaws are quite effectual, are social bees but with the 

 other habits of the solitary kinds. 



The organic substance of a plant transformed into the or- 

 ganic substance of an insect or related creature loses none of 

 its food value; indeed in its new form it is even more desirable 

 as food. Vast hordes of insects and their relatives of every 

 major group subsist entirely or partially on other insects, which 

 latter have been nourished by the plants. 



All spiders (aside from certain mites), scorpions and centi- 

 pedes are throughout their lives carnivorous, catching and 

 devouring insects of various sorts, and sometimes other crea- 

 tures; for instance, giant spiders will kill and eat small birds, 

 and giant centipedes catch lizards and are very fond of mice. 



Most of the gall wasps and many gall midges, some saw- 

 flies, a few agromyzid and trypetid flies and fungus gnats, some 

 mites and plant-lice, and some of the small moths by stinging 

 or otherwise injuring a twig or leaf cause a pathological swell- 

 ing called a gall which provides food for the grub inside. This 

 grub may be accompanied by "guests" of other types, as well 

 as serve as food for parasites. 



Great numbers of insects subsist upon decaying vegetable 

 matter, especially when very moist, including many sorts of 

 flies and beetles, spring-tails and crickets, and most millepeds. 

 It is rather curious that nearly aU blood-sucking flies except 

 the horse-flies, some mosquitoes, and the tsetse, and all the 

 fleas, when maggots, live on or in the ground, or sometimes in 

 water, peacefully feeding on decaying vegetation. 



Thus every part of a green plant is eaten by a large variety 



