SCALE INSECTS OF IMPORTANCE 



309 



female, in from 33 to 40 days. The detailed studies made at Washing- 

 ton show that four full generations are developed normally in that lati- 

 tude and that there may be a partial fifth. The production of a few 

 young each day for some six weeks leads to a confusion of broods toward 

 the end of the season, and their exact number can not be determined 

 without special study. This insect breeds in the vicinity of Albany from 

 the latter part of June through October. After making due allowance 

 for the difference in latitude and the slower development in cooler 

 weather, we can hardly expect more than three full generations normally, 

 with a possibility of a fourth under exceptionally favorable conditions. 

 This is confirmed by the studies of Prof. V. H. Lowe at Geneva. He 

 found the average duration of the period of growth to be 49J days, which 

 gives just about time enough for three full generations during the growing 

 season. 



Food plants. This insect has been recorded on a considerable num- 

 ber of food plants, and its ability to live on so many varieties adds very 

 much to the difficulty of exterminating or controlling it. The following 

 is a list of food plants, as compiled by Dr Lintner, with a few additions 

 by Dr Howard and from office records. 



Tiliaceae 



Linden 

 Celast rac eae 



Euonymus 

 Ro saceae 



Almond 



Peach 



Apricot 



Plum 



Cherry 



Spiraea 



Raspberry 



Rose 



Hawthorn 



Cotoneaster 



Pear 



Apple 



Quince 



Flowering quince 

 Saxi fragaceae 



Gooseberry 



Saxi fragaceae {continued) 



Currant 



Flowering currant 

 Eb en aceae 



Persimmon 

 L egu minoseae 



Acacia 

 O 1 eacea e 



Lilac 

 Urticaceae 



Elm 



Osage orange 

 J uglandaceae 



English walnut 



Pecan 

 Betulaceae 



Alder ? 

 Salicaceae 



Weeping willow 



Laurel-leaved willow (from 

 Asia) 



