MAN IN A WORLD OF INSECTS — DE LONG 435 



I was assigned the task of finding how much leaf tissue a tobacco 

 horn-worm larva would consume between the time it hatched from the 

 egg and the time it became a quiescent pupa. From the data I 

 obtained and from the studies of subsequent workers, we can conserva- 

 tively say that a single larva (tobacco worm) consumes in 28 days of 

 larval growth, food weighing approximately 50,000 times its birth 

 weight, and the larva increases in size during this period approxi- 

 mately 12,000 times its birth weight. Equally surprising is the case 

 of a silkworm larva which consumes its weight in food each day. 



5. To these characteristics should be added the factor in insects 

 of great biotic potential — the power of the insect to reproduce rapidly 

 and establish enormous populations. This potential factor has been 

 stressed by the theoretical estimates of many of our honest and repu- 

 table entomologists, who estimate, for instance, that imder optimum 

 conditions a single cabbage aphis together with its accumulating de- 

 scendants could, if enough cabbage were available, produce in a single 

 growing season enough aphids, weighing one milligram each, to form 

 a mass weighing 822 million tons or 5 times the weight of the total 

 human population of the world. "Wliile this does not occur, the 

 potential danger is always present in man's world of insects ; and here 

 or there, from time to time, where environmental resistance is re- 

 strained, the chinch bug, the Japanese beetle, the Mediterranean fruit 

 fly, or some other specific form, will produce populations which get 

 out of hand in spite of man's knowledge and continued efforts to 

 subdue them. 



Consider the potential of a common rainbarrel, which has been 

 observed to produce in excess of 100,000 mosquitoes in a single season. 

 Regarding this potential, we should bear in mind that an average of 

 only 1 percent of the previous season's populations survives the period 

 of wintering. 



Certain insects, such as the digger wasps, in the absence of food 

 preservation by low temperatures, habitually paralyze their prey by 

 stinging them and then depositing their eggs upon these victims which 

 are used to provision their galleries or burrows. In case these para- 

 lyzed insects should die the venom acts as a preservative and they will 

 not decompose for periods of several vv-eeks or even months. 



The insect heart is a very unimportant structure in connection with 

 respiration or oxidation. So heart disease, the great killer of humans, 

 could not occur in an insect. In like manner, insects have no lungs, no 

 liver, and no kidneys. The respiratory system composed of a complex 

 network of tracheal tubes is adapted to all types of aquatic life and is 

 tolerant of both air and vacuum pressure and of high altitude flight, 

 and is more tolerant to radiation than vertebrate animals. 



Also, consider the fact that in insects the infants, when born, usually 

 take care of themselves ; there is seldom parental care. Add to this 



