428 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1962 



manufacture could not be obtained from Europe. The pharmacists 

 then became disturbed when they learned that different species of 

 beetles contained different percentages of cantharidin and that the 

 species in the United States yield very small percentages. Canthari- 

 din has not been, and apparently cannot be, produced on a commercial 

 scale from native blister beetles. 



Another example of the value of insects in medicine is the use of blow- 

 fly larvae to render aseptic and hasten the healing of surgical wounds 

 caused by osteomyelitis. In a field dressing station in France during 

 World War I a young surgeon observed severe shrapnel wounds 

 containing infestations of fly maggots and noted the subsequent rapid 

 recoveiy of the soldiers so infested. After returning to the United 

 States he was responsible for the experimental treating of wounds 

 with fly larvae of Lucilia serricata and Phormia regina reared under 

 aspetic conditions. Through this treatment a therapeutic agent, 

 allantoin, has now been developed and fly maggots are no longer being- 

 used. At present allantoin is being used in the treatment of osteo- 

 myelitis and other deep-seated wounds in which there is decaying 

 tissue. The fact remains that it was through the use of fly maggots 

 and a study of their physiologic action that a modern medical treat- 

 ment was developed for a condition which was previously very difficult 

 to cure. 



Insect parasites and predators. — Some of the most valuable insects 

 are those which live upon or within other insects, particularly noxious 

 plant-feeding species, and thus destroy them. We usually classify 

 these as parasites and predators. Both types are important, although 

 the parasites are much more complex in their biology and adaptations. 



Predation is a common mode of sustenance of many types of 

 animals, including man. The development of predation in insects is 

 hard to trace, but we know that it existed in certain forms such as the 

 dragonflies, which were major types of insects in the late Carbonif- 

 erous and early Permian periods. The habit of predation is found 

 generally throughout the insect orders. In many species and groups, 

 however, predation may not be beneficial to man. This is especially 

 true in the case of the large group of aquatic predatory insects. Even 

 when the predatory habit is beneficial, such as the aphid-feeding habit 

 of the tree crickets, the benefit is often offset by an injurious habit 

 such as egg-laying in twigs or stems w^hich causes untold injury to 

 the plant or crop. 



There are many groups in which predation brings enormous value 

 to man. This is particularly true of those insects which feed upon 

 colonies of aphids or attack caterpillars upon the ground. Most of 

 these have insatiable appetites and are therefore important factors in 

 the control of the insects upon which they prey. The following data 

 will bear out this statement: 



