MAN IN A WORLD OF INSECTS — DE LONG 437 



and the water released in the body from this source is conserved by 

 the process of excretion and the production of dry fecal pellets. 

 Stored-grain insects conserve water in a similar way. 



Gall insects, belonging to several orders, demonstrate another in- 

 teresting phase of nutrition and interrelationship. In this case the 

 insect produces a stimulus which is so specific that each individual of a 

 gallmaking species will cause the plant to produce the same type of 

 abnormal growth, inside of which the immature insect feeds, grows, 

 and develops to maturity. Conversely, every different species of gall- 

 maker on the same plant will stimulate the plant to produce its own 

 specific and uniform type of abnormal growth. 



One of the most amazing adaptations is found in the ephydrid flies 

 which live in saline, alkaline, or other solutions of extreme degree or 

 variation. Certain of these occur in ocean water, in the Great Salt 

 Lake, in the Bohemian salt mines, in pools of crude oil in California, 

 and some have been found living in medical-school cadavers preserved 

 in strong solutions of formaldehyde. 



An interesting survival factor is also displayed in the sexton beetles 

 belonging to the Silphidae. These live in the bodies of exposed dead 

 animals. The eggs are laid and the larvae develop in these carcasses, 

 but the larvae must have soft, moist tissues to complete their growth. 

 In hot dry weather these carcasses will desiccate rapidly, but the 

 species is preserved by the action of adults, which dig the soil from 

 under the carcass and gradually, but rather quickly, bury it. 



To the best of our Imowledge the caddis-fly larvae were the first 

 organisms to demonstrate the use of nets to capture aquatic micro- 

 organisms. The dragonfly naiads, by the intake and repulsion of 

 water to bathe the gills in the rectal cavity, gave us the first example 

 of jet propulsion; and the paper wasps of the hornet group were the 

 first to make paper from wood pulp. 



NATURAL BALANCE 



It is impossible to predict what role the insects might have played in 

 the world without the advent of man. There is no question but that 

 they had existed for millions of years and had become well adapted. 

 Our observations, however, of areas of the world uninhabited by man 

 have proved that natural conditions are usually well balanced until 

 man's arrival. The number of insects and their interrelationships, 

 parasites, predators, etc., the diversity of j)lants, and many other fac- 

 tors keep populations well balanced. '^'S^ien man arrives he cuts down 

 forests, cultivates fields containing many kinds of wild plants, and 

 changes the fields to extensive acres of one kind of plant or crop. This 

 upsets the balance and produces extensive populations of what we 

 term economic insects. 



