256 FOREST ENTOMOLOGY. 



less to winged specimens is the result of the short period necessary 

 for the ushering in of a fully developed fresh brood, which will adapt 

 themselves to natural changing conditions. In other words, the 

 newly born brood will move to new quarters either in search of food 

 or warmth. And here comes in a very common but erroneous notion 

 — viz., that the sudden appearance of " blight " is due to " east 

 winds." J^ow the fact is that the proverbial east wind has simply 

 assisted the winged aphis, which, after all, is but poorly adapted for 

 locomotion, to move from his native land to "fresh fields and pastures 

 new." 



Winged forms are known at an early age as apterous larvae, the 

 "pupal" stage being that period when the wings are half-grown. 

 Some species pass through these metamorphic stages before their life 

 cycle is complete. Thus apterous larvie, semi-winged pupae, and 

 winged imagines may be constantly found throughout the summer 

 season on the food-plant. 



In many species both apterous and Avinged females produce living 

 young, but, according to Buckton and other observers, the pupae never 

 give birth to young. There are two classes of females apart from 

 apterous and winged ones — viz., oviparous and vivij^arous, the first 

 reproducing themselves by eggs, the second by living young. It is 

 asserted by many practical workers that the oviparous never becomes 

 viviparous, or vice versa, the same individual aphis never producing 

 eggs and living young. 



The difference between the deposition of eggs and the production of 

 living young on the part of the respective female insects would appear 

 to be simply a question of time and stage of reproduction, but it affords 

 a subject for actual investigation by dissection and serial section-cutting, 

 in order to ascertain the morphological difference between oviparous 

 and viviparous organs. 



To the student of forest entomology it is not only essential to make 

 a detailed study of the life -history of the various species as found 

 on trees, but it is indispensable to study the species found on almost 

 every plant, inasmuch as we get migratory species and dual or 

 multiferous food-plants of certain species. Thus, for example, we get 

 the hop aphis, the larch and spruce aphis, mealy plum aphis, together 

 with root and trunk forms constantly changing from food-plant to 

 food-plant. It is therefore obvious that this is a good case in point, 

 showing that it is most essential for the economic entomolosrist to 



