12 



Fig 



-Pulvinaria in n u m ei 



abilis: young hibernating 

 female, from above — greatly 

 enlarged (original). 



the abdomen; the claw of the tibia is lost, and. between the posterior 

 tubercles has appeared the stout, rudimentary style. The true pupa, 

 specimens of which were also found as early as July 26, needs no 

 description. The adult males began to issue on the same date for cer- 

 tain specimens, and as early as August 6 females had begun to migrate 

 to the trunk 5 by August 21 all of the young 

 females had left the leaves and migrated to the 

 stem. It should be stated that these observa- 

 tions of 1899 were made upon a young potted 

 tree in the insectary. The temperature, how- 

 ever, Avas practically the same as out of doors. 

 So great had been the parasitism of the insect 

 outside, that it was found necessary to make 

 observations on potted trees under glass both 

 in 1898 and 1899 in order to preserve the species 

 for observation. 



Briefly then, there is one annual generation: 

 the young hatch in early summer and settle 

 upon the twigs; the males appear at the end of 

 August and early in September; they fertilize 

 the females, which migrate to the twigs, where 

 they remain unchanged through the winter, rapidly swelling in the 

 spring and forming the egg mass in early summer. 



The insect is a notable one from its frequent sudden appearance in 

 great numbers. After being almost unnoticed for 

 a series of years it will appear in excessive num- 

 bers, apparently injuring shade trees to a consider- 

 able extent; then, without insecticide measures 

 having been employed, it will as quickly disappear. 

 These sudden appearances and disappearances are 

 due very largely to fluctuation in numbers among 

 natural enemies of the species, as will be shown 

 in the following paragraph. 



Natural enemies. — Birds destroy the full-grown 

 scales, although one would hardly suppose a 

 mouthful of wax to be very palatable. The writer 

 has often observed the English sparrow apparently 

 feeding upon this species. 



The usual predatory insects which feed upon 

 other scale insects seem equally fond of this species, 

 and the twice-stabbed ladybird (Chilocorus bivul- 

 nerus) is one of its especial enemies, as was long- 

 ago pointed out by Miss Emily A. Smith. The 

 little insignificant ladybird beetle, known as Hyper- 

 aspis signata, is also a common predatory enemy of the species. 



In 1879, in Washington, D. 0., it was found that the most effective 

 enemy of the scale was a predatory caterpillar described at that time- 

 by Professor Oomstock as Dalcruma coccidivora. This caterpillar flour- 



FlG. 6. — Pulvinaria innu- 

 merabilis: gravid female, 

 greatly enlarged, before 

 commencing to secrete 

 egg sac in the spring 

 (original). 



