NEW JERSEY 



AGRICULTURAL EXPERIMENT STATIONS 



BULLETIN 332 



SOMP] STUDIES ON THE EGGS OP IMPORTANT 

 APPLE PLANT LICE 



By 

 Alvah Peterson, Ph. D. 



Introduction 



This paper treats of some recent investigations on the strueture, 

 behavior and susceptil)ility of the eggs of three important aphides 

 found on apple trees, Aphis ai'eiue Pabricius, Apltis pomi DeGeer, 

 and Aphis sorhi Kaltenbaeh. It takes up a thorough discussion of 

 the results obtained during the season of 1916- 17 which were pub- 

 lished in brief form in the Journal of Economic Entomology for 

 l^ecember, 1917. It also includes a report on the extensive experi- 

 ments and observations conducted during the past season (1917-18) 

 on the eggs of A. avcnce. 



A considerable amount of work has been conducted by various 

 investigators on the effect of the more common contact insecticides 

 on aphid eggs, but few if any good reasons have been advanced 

 which explain the varying results. To get at the causes for these 

 results involves a careful study of the physical and chemical struc- 

 ture of the egg, particularly the egg shell and the response of the 

 egg to various stimuli such as temperature, moisture and chemicals. 

 Studies pertaining to all these points have not been made, but some 

 have been conducted, viz., the gross morphology of the egg coverings 

 and their behavior previous to the emergence of the nymph, the 

 susceptibility of the egg to variations in temperature and to differ- 

 ent percentages of moisture, and the physical changes produced on 

 the coverings of the egg by a number of common insecticides and 

 other chemicals, and also the influence of these substances on the 

 normal percentage of hatch. 



The eggs of the three species of apple plint lice were collected 

 from different orchards throughout the state of New Jersey during 

 the past two seasons. In 1916-1917 the eggs of the so-called apple- 

 bud-aphis, oat-aphis, or European grain-aphis, A. avence, were 

 abundant in the orchards on the College Fann and at John II. Bar- 

 clay's orchard, near Cranbury, N. J. During the same season the 

 eggs of the rosy aphis, A. sorhi, also occurred in these orchards, but 

 in no collection did they exceed 15 per cent of the total number. The 



