436 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1962 



the fact that there is no old age in insects. When their work is finished, 

 they die. There is no retirement, no social security, no old-age pen- 

 sions, and never a feeble grandparent. All these problems have solu- 

 tions in a world of insects as a part of their adaptation. 



ADAPTATIONS 



Not only did man find these populations of insects in the world, 

 but he also found extreme adaptations of these species by millions of 

 years of survival selection. The extent to which insects will become 

 adapted is amazing, and often shocking, at least when you use your 

 imagination as to what might happen in the future. These adapta- 

 tions occur in morphology, all phases of the biological cycle, habits, 

 and physiology. The following are a few examples of these 

 adaptations. 



The legs of insects are adapted in various groups for running, swim- 

 ming, digging, grasping, and holding prey or, in the case of blood- 

 sucking lice, grasping and holding onto the hairs of mammals. In 

 the case of surface-swimming gyrinid beetles, their eyes are divided 

 so that one portion of the eye is above the surface of the water and the 

 other is below. 



In many insects which have hypermetamorphosis, the larva when 

 first hatching from the egg may have well-developed legs and be 

 able to seek out an egg mass upon which to feed ; but when moulting 

 to a second instar the legs become quite small and inadequate for 

 locomotion. This condition is also seen in the scale insects which 

 have an active first instar crawler stage and then become sessile and 

 lose their legs in the second and succeeding instars. 



Many interesting adaptations are seen in egg production. In some 

 insect parasites we have a condition which is known as polyembryony. 

 The female lays a single egg which eventually produces many individ- 

 uals. In the cannibalistic aphis lion the survival factor is apparently 

 accomplished by the eggs being laid on stalks, and thus brothers and 

 sisters are protected from the first of the brood to hatch. Females of 

 the giant waterbug, genus Ah edy-s, glue the eggs to the back of the male, 

 where they remain until hatching. 



Certain insects are adapted to extremes of climate. The grylloblat- 

 tids prefer temperatures of 0° C. and apparently are unable to live at 

 temperatures which are more than a few degrees from this point. 

 They normally occur at the edge of melting glaciers. At the other 

 extreme, certain insects live in hot springs with temperatures of 120° 

 to 124° F. 



There are many diversified adaptations in feeding habits and phys- 

 iology among insects. The clothes-moth larvae feed upon animal 

 fiber (carotin) only and never have available water as such. The 

 water needed by the body is obtained through metabolic processes. 



