EXPERIMENT STATION BULLETINS. 18r> 



of the codling-moth very forcibly to our notice. Furthermore, in making recom- 

 mendations for the treatment of trees, it became apparent that many points in 

 the life-history of the creature were only to be guessed at in this, the most 

 northerly State of the middle United States, where the pest is common. It is so 

 important indeed that the depredations of all other apple Insects sink into insig- 

 nificance when compared with it, — so serious that half or more of the apple crop 

 is sacrificed annually to its inroads. Furthermore, conditons vary so widely ia 

 the great apple growing regions of our country, that data collected in different 

 localities and in different latitudes, might be so widely at variance that they 

 would be of little value except in the immediate regions where they were 

 obtained. 



Early in the spring of 1903, it was decided to start a series of observations 

 which should, if possible, give us reliable information on the number of broods, 

 the times when they occur, and the effects of a spray applied just when the 

 second brood of larvae were ready to enter the fruit. These observations have 

 been carried on over a space of two seasons, and the following -results obtained: 



In order to understand clearly the sequence of the broods, it will be necessary 

 to review briefly the life-history of the creature. 



The winter is passed in the larval condition enclosed in a cocoon of white 

 silk, in which is bound considerable frass or chew-ed up fibre. This winter cocoon 

 is quite thick and heavy and ordinarily is to be found neatly hidden aw^ay under 

 loose pieces of bark, beneath fence-rails, under branches and in similar places. 

 Often the cocoon possesses only a very thin film of silk next the wood and the 

 bark, most of the material being used in making a ring between these two sur- 

 faces. The cocoon is about half an inch long and oval in form, just occupying 

 the space allowed. Often, a tube extends from the outer more roomy part under 

 the flake, down to the thin part of the wedge-shaped opening where the cocoon 

 is placed, the larva in such a case, having commenced to spin where the space 

 was too large, had crowded in toward the narrower part as it built. 



Diligent search was made for these cocoons, in the spring of 1903, and two 

 in good condition were found. A quantity of empty ones came to light, the 

 larvae having been picked out by birds during the winter. These two cocoons 

 were placed in cages and while their transformations may have been somewhat 

 hastened by reason of being brought into the house, there is reason to believe 

 that adults out of doors emerged soon afterwards. The two emerged on May 

 22. On June 12, I found eggs and young larvae. It may be well to state that on 

 May 25, the blooms on the trees had practically all fallen, for on that date the 

 spraying of the College orchard commenced. 



The codling-moth, as everyone knows, has very poorly defined broods, the 

 members of a single generation becoming adults over a considerable range of 

 time, and not emerging all together as in the case of the canker-worm and many 

 other insects. The most that could be hoped for would be to ascertain the top 

 of the wave of prevalence of the insect in each stage, thus it is very desirable to 

 know just when the greatest number of the eggs hatch, when the spinning of the 

 cocoons is most actively carried on, etc., and these things for each generation. With 

 these facts at hand, it is much easier to so time the application of the sprays as to 

 catch the greatest number of young larvae just entering the fruit. 



Simpson, in his bulletin number 41, of the Division of Entomology, gives 

 fifty-five to fifty-eight days as the average time required for the moth to com- 

 plete its life cycle, and counting backward from June 12, the time when the 

 eggs and young larvae predominated, we find that our two moths probably emerged 

 before the majority of those out of doors. We have set June 1 as about the 

 right time. Counting ahead 57 days, w^e get the date of the emergence of the 

 adults of the second generation on about July 27, and in our cages containing 

 freshly collected cocoons, we get the greatest number of adults at this time. 



A schedule made up partially from our observations in 1903, and partly from 

 calculations, using fifty-seven days as an average time for the completion - of 

 the life cycle, would look something like this: — 



FIRST gem:u.vtion. 



First adults, May 22 (blooms falling about May 25). 

 Most adults, June 1. 

 Most eggs, June 9. 



24 



