168 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 4 



Rubbing the trees is a very good method of destrojdng the Aphis 

 on the tops, especially when care is taken to get into all the crevices. 

 Observation in the laboratory shows that Aphis which are removed 

 while they have their beak in the wood, perish because the beak 

 is broken in most cases. And in no instance did any Aphis so removed 

 establish itself upon the plant again and live. 



It takes the young about ten days to come to maturity, during 

 which time it molts four times. In the months of August and Sep- 

 tember an adult brings forth from two to three young, but the rate 

 of increase seems to be greater in the spring. 



The first winged forms were noticed in the laboratory on September 

 19. During October and the first part of November large numbers 

 of winged forms appeared. On December 6 the last winged form 

 appeared in the laboratory. The winged forms do not produce any 

 woolly secretion. Not every colony in the laboratory produced 

 winged forms. Several colonies were observed where nearly all of 

 the forms produced wings and after the death of the old apterous 

 forms only a few wingless young remained to perpetuate the colony. 

 In some colonies, on the other hand, only a few winged forms were 

 produced. 



The offspring of these winged forms are the true sex forms. A 

 number of these winged Aphis were isolated, each one being placed in 

 a separate tube. It was found that they begin to reproduce on the 

 sixth day. This gives the date for the appearance in the laboratory 

 of the first sex forms as September 25. Many of them died without 

 producing any young. Out of a series of nineteen only eleven repro- 

 duced, as is shown by the table on page 169. 



These true sex forms differ from the agamic forms in that they 

 produce no woolly secretion and have no beak. This latter difference 

 is apparent from the very first, because the young' of the common 

 forms have a beak longer than their body. Since these true sex 

 forms have no mouth-parts they cannot take any food, yet they pass 

 through four molts, which seems to require about eighteen days. 

 The male increases very little in size, and increase in the female is 

 probably due mainly to the development of the egg. It may be added 

 here that both sexes remain wingless throughout life. 



The sex forms differ among themselves in size and color. From 

 the very first the male is smaller than the female, and in the adult 

 form is not much more than one third the size of the latter. The 

 male is throughout life of an olive green color, while the female retains 

 the light chocolate brown. 



Both sexes are quite active in the early part of their life, but ap- 

 parently they seek only a favorable hiding place, where they can remain 



