8 Bulletin 332 



binocular microscope. Before starting or spraying any set of twigs, 

 all eggs on each twig, 8-12 inches long, were carefully ohsc^rved and 

 their condition noted. If any egg was shriveled or liatchetl or ap- 

 peared to be abnormal in any respect, it was removed; thus in the 

 various experiments only normal-appearing eggs were used. Every 

 twig bearing five or more normal eggs (in exceptional cases 200 eggs 

 of A. pomi were present on one small twig) nas given a string tag, 

 and on this tag was written the number of the experiment, the 

 source of the material, the treatment given, tlie number of nonnal 

 eggs at the beginning of the experiment and in many cases the num- 

 ber of discarded abnormal eggs, and hatched eggs, if such were 

 present. 



The various common contact insecticides, lime-sulfur, miscible 

 oils, laundry and fish-oil soaps, nicotine sulfate and nicotine resinate, 

 and other chemicals such as crude carbolic acid, phenol c. p., meta 

 cresol c. p., ortho cresol c. p., para cresol c. \\., sodium hydroxide, 

 sodium chloride, sodium sulfo-carbonate, pyridine solution, 

 etc.. were applied to the twigs by means of a small atomizer 

 which was connected with a foot pump. The atomizer gave a coarse 

 spray and the force of the spray was weak, for the greatest pressure 

 coukl not throw the material over three feet. The twigs at the time 

 of spraying were held a few inches from the tip of the atomizer, and, 

 so far as possible, all sides of the twig and all the eggs were hit with 

 the spray. Probably not one tg^ out of a thousand was missed. 



Experiments with tlie various contact insecticides and chemicals 

 during 1916-17 were coiulueted in tlie greenhouse on the eggs of 

 ^L. avena', and out-of-doors with the eggs of all three species. 

 In 1917-18 a duplicate set of experiments was started in the green- 

 liouse and out-of-doors with the eggs of A. uvcikv, h\\\ a sliortage of 

 coal during the month of February ma(l(> il necessary to close the 

 greenhouse. The twigs were brought into the laboratory from the 

 greenhouse and ])laced in a large tin (•oiii|)artiiient, ])ut the results 

 o])tained from these experiments were not as satisfactory as they 

 would have been under greenhouse coiiditioiis, consequently tliey 

 have been largely omitted from this paper. Since it was necessary 

 to close down the greenhouse, a more strenuous effort was nuule to 

 run a larger number of experiments under out-of-door conditions. 

 The twigs used in the experinu^nts in 19U)-17 in the greenhouse 

 were placed in tumblers and these wert' set on tanglefoot paper in 

 order that the nymphs might not escape. The temperature of the 

 greenhouse averaged 65° F., and the humidity was about 75 per 

 cent most of the time. In all the out-of-door experiments conduct- 

 ed at the laboratory the twigs bearing tlie eggs were .suspended on 

 wires which extended across the tops of large empty wooden boxes. 

 These boxes were located in an open place near the laboratoi-y and 

 completely exposed to all conditions ol' the weather, thus duplicat- 

 ing, as nearly as possible, the orchard environment. The results 



