12 PROTECTION OF PLANTS — 1924-25 



living its life at the expense of its forebears, after hatching from the egg, it, in 

 its own brief time, accumulates for itself all the materials for the growth of a 

 lifetime. It is a model of fitness and efficiency. It is of about the optimum size 

 for taking advantage of scattered food supplies, as the world offers them — 

 big enough for efficient operation — not so big but that a livelihood may be 

 found in numberless places. It is a simplified arthropod, with all redundant 

 and unnecessary parts removed. No cumbrous parts of the adult insect appear: 

 nothing appears but what is necessary for getting a living and keeping alive; 

 feeding organs and means of keeping to cover; that is all; an irreducible mini- 

 mum ! 



The larva represents a segregated period in the life history of the insect — 

 a period of food accuinulation and growth. The complicated organs of the adult 

 insect, wings, antennae, etc., are not seen in the larva. They are present as 

 small rudiments, biding their time, waiting for a more favorable season for 

 further development, waiting on the more important and more pressing business 

 of food-getting. The larva is preeminently fitted for "making hay while the sun 

 shines". More than any other animal of comparable size it lives on perishable 

 and transient foods, and it lives among a host of greedy competitors. It must 

 work fast, and lay up stores. It uses a little food to build such organs as are 

 immediately necessary; the remainder it stores as fat. When it is fully fed it is 

 largely a mass of fat, with a few old and more or less effete nutritive and motor 

 organs disposed through and around the body, and with only the rudiments 

 of adult organs. 



Then comes transformation. The larva goes into retirement, and ceases 

 activity. The pupal stage is entered upon. Another marvel ensues. The animal 

 though grown to its maximum size, now returns to a condition comparable to 

 that of an embryo. The rudiments of the adult organs begin to grow. They 

 feed upon the store-up fat, much as in the egg the initial larval organs fed on 

 the yolk therein. Though these rudiments are scattered about the body, they 

 are bound together with the thread of life ; they grow and shape themselves and 

 and organize into the perfect insect, with all its organs, all its powers, and all 

 its endowment of inerited behavior. 



Clearly the larva would be a helpless, hapless, hopeless thing without the 

 nstinctive aid of the mother insect to place it in reach of its proper food. 



Such is metamorphosis at its best, truly a world phenomenon, and so 

 manifest only in a portion of the group of insects, a life cycle broken into two 

 periods, corresponding to the two great undertakings of life, growth and repro- 

 duction, and separated by a stage for the making over of the one into the other. 



Of all biological expedients metamorphosis is clearly one of the most 

 successful if success is measured by dominance. The group of insects outnum- 

 bers in species all other kinds of animals put together, and four orders of insects 

 in which metamorphosis is completest are so preponderant that all the others 

 taken together seem but a handful in comparison. These four are the Lepidop- 



