34 Journal of the Mitchell Society [December 



Life Histories. 



The general phases of the Hfe histories of insects are usually well 

 known but even here we find that there are many popular misconcep- 

 tions. McCormack tells of a physician who laughed at the notion 

 that house flies are but one stage of maggots for said he, "Have I not 

 often seen little flies coming out of the ground in the spring." One 

 of our largest potato growers believed that I was trying to fool him 

 when I told him the "soft shelled potato bug" is but the grub of the 

 "hard shelled potato bug" and he was not convinced until he had 

 tried the thing out and carried the grubs through their changes to 

 pupae and then to adults. Afterwards he said to me, "That is the 

 most valuable lesson I have ever learned on the farm, for it has 

 taught me that I have not seen what is about me every day." 



We are inclined to smile at the ignorance of people in general as 

 outlined by such examples as those quoted above but before we allow 

 our smiles to become too broad perhaps it would be better to inquire 

 into our own knowledge. We know or think we know the life his- 

 tories of a few insects scattered from one end of the insect kingdom 

 to the other but this knowledge is based chiefly on the study of a few 

 economic forms. And too frequently these life histories have been 

 worked out in our more northern states and apply only imperfectly or 

 not at all to our southern conditions. 



The wonders in the adaptations for carrying on the life cycle of in- 

 sects are almost beyond belief and I wish that I had the space to re- 

 count many of them but time will permit citing only a very limited 

 number. The time involved in completing a life cycle is apparently 

 as varied as the species of insects themselves. I need only remind you 

 of the cicada on the one hand, whose cycle covers seventeen years, 

 while on the other hand we have the house fly with a complete cycle 

 every nine to fourteen days, in the warmer parts of the year. 



The complexity of the cycle is also very much involved. We have 

 insects like the fish moth with no changes or metamorphosis on the 

 one hand while on the other we have forms like the blister beetles with 

 no less than eight distinct stages in its cycle. Between these two ex- 

 tremes are all grades of forms with almost every conceivable relation. 



The following table will make these relations clearer than they 

 would otherwise be: 



