APPENDIX. 311 



arsenic. The quantity found was scarcely enough to weigh, and it seemed 

 as though it were not enough to l-cill the little apple worms. But when one 

 remembers that only four or five gallons of the spray are usually applied to 

 a whole tree, and when this is divided up among the millions of leaves and 

 the thousands of apples on that tree, it is easy to see that the amount of 

 arsenic which a single fruit would get, or even fifty of them, would be 

 exceedingly small. Would it be enough to kill the j'oung apple worms 'i 

 Careful experiments have shown that it takes much less poison to kill cater- 

 pillars when they are small : and as the young apple worms are scarcely a 

 sixteenth of an inch in length when they begin feeding in the calyx cavity, 

 it would take only an infinitesimally small amount of arsenic to kill them.* 



The above fact^ and observations lead us to believe that in applying a 

 poisonous spray soon after the blossoms fall, we deposit some arsenic in the 

 calyx cavity, where nature kindly takes care of it for us until ten days or 

 two weeks later, when the little apple worm includes it in the menu of his 

 first few meals. Furthermore, th^ poisoning of these young worms which 

 enter the developing fruit in the spring, seems to be the only way and only 

 time that the insect is or can be the most successfully reached with the 

 spray; as the worms sometimes eat through into the calyx cavity from the 

 outside at the base of the lobes, and as some of the poison often lodges here. 

 l>ossibly a few of them get enough poison to kill them at this point. Not 

 enough of the spray can be made to stay on the surface of the fruits then or 

 at any subsequent time to reach one in a hundred of the worms which enter 

 elsewhere than at the blossom end. Put in another way, the above facts 

 mean that we can hope to reach with a poison spray only those apple worms 

 which enter the blossoqj ends of the forming fruits in the spring. To do 

 this, the application must be made soon after the blossoms fall, when the 

 calyx is open, as shown in Fig. 145. If we wait a few days until the fruit 

 has reached the condition shown in Fig. 14«). or still later as at a and h in 

 Fig. 131, it will be too late. We can conceive of no possible way in which 

 a majority of the fifteen or twenty per cent, of the worms which enter the 

 fruit at some other point in the spring, and all of the worms of the subse- 

 quent broods, can be effectively reached with the poison spray. 



Thus, while the spraying method is very effective, it can never prove a 

 perfect penacea. especially where there are two full broods or more of the 

 insect in a season. However, it is a great improvement over the old band- 

 ing method, for with the spray we kill the worms before they fairly begin 

 their destructive work, thus saving the fruit they would otherwise ruin with 

 an ugly worm hole. Our observations indicate that the little worms do no 

 feeding on the outside of the fruit except just enough to make a tiny entrance 

 hole into the flesh or into the calyx cavity. If it were not for their habit of 

 feeding in this blossom cavity for a few days, it is doubtful if spraying would 



*Mun.«on has figured out how much i>oison would be liable to stay on one apple, 

 allowing two sprayings of two gallons each to a tree. His figures show that the amount 

 of poison per fruit" would be less than three one-thousandths of a grain. 



Others have made chemical analyses of the blossorii ends of apples, and report no 

 traces of arsenic, but their material was not taken until several weeks after the spray- 

 ing was done (and it may not have been done when the calyx cup was open ). hence 

 could be of little value to determine the point in question. 



