484 REPORT OP THE COMHISSIONER OF AGRICULTURE. 



nest, tliiis indicating that the young had been accidentally brought 

 there and in considerable numbers by the old birds. There is no 

 doubt also that the irrigating ditches have a very marked influence 

 on the spread of the species, as many of the ditches pass under in- 

 fested trees, and the waxy secretion serves both to protect the insect 

 from the water and to facilitate floating. 



While, therefore, the gradual spread from orchard to orchard is in 

 the main through the agency of other flying insects and gossamer 

 spiders, yet the transportation of the pests to long distances must 

 necessarily be effected through the agency of high winds, birds, and 

 man in commercial intercourse, the latter being probably the only 

 means by which the species have been introduced from one country 

 to another separated by wide ocean areas. 



NATURAL ENEMIES. 



Birds. — Tlie na,tural enemies of the Cottony Cushion-scale seem to 

 be very few in number, not only in California but also in South 

 Africa and New Zealand. In South Africa the only bird which is 

 recorded as feeding ujoon this scale is the common "White Eye" 

 (Zosterops capensis), and this is given by Mr. Trimen upo]i hearsay 

 evidence only: " I have not noticed any of our small birds attacking 

 the Dorthesia, but Mr. C. B. Elliott tells me that his boys have ob- 

 served the little 'White Eye' * * * pecking at them." From 

 what vre have been able to learn of the habits of this bird, however, 

 we are inclined to think that it is attracted rather by the abundant 

 secretion of honey-dew and the minute insects caught in it than by 

 the scale-insects themselves. 



Neither Mr. Coquillett nor Mr. Koebele observed any bird feeding 

 upon it. The reason for this exemption is probably the copious se- 

 cretion of wax, which is doubtless distasteful. Several reliable per- 

 sons report that ducks and chickens feed greedily upon those scale- 

 insects which are dislodged from the trees. On one occasion a brood 

 of six young ducks gorged themselves upon scales which had been 

 washed from the trees with pure water, and on the same day two 

 ducks died. On the day following three more died, while the sixth 

 recovered after an illness of several days. This disastrous effect was 

 probably due to the greed with which the scales were eaten, as they 

 were said to produce no such result with chickens which ate them at 

 the same time. 



Predaceous Insects. — The only predaceous insect observed by 

 Mr. Coquillett to feed upon the Cottony Cushion-scale was the larva of 

 a species of Lace-wing fly {ChrysojJa sp.), which was not bred and 

 cannot be named more exactly. 



The Ambiguous Lady-bird (Hippodamia amhigua) has been no- 

 ticed feeding upon the eggs v/hen they were exposed to view \)j the 

 egg-sac being broken open; but neither this nor any other species of 

 Lady-bird was seen to feed upon the adult insect, although commonly 

 attracted by the lionej^-deAv secreted. 



Among the predaceous insects found by Mr. Koebele and sent to us 

 for study we may mention first the larva of a small moth (Blasto- 

 basis iceryceeUa n. sp., Plate III. Fig. 3), although as yet we are not 

 certain that it ordinarily ju'eys upon the living and uninjured scale- 

 insects or their eggs. Like certain other so-called predaceous Lepi- 

 doptera, it may be attracted primarily by tiie waxy secretions of the 

 bark-lice, and only incidentally destroy the insects and their eggs. 



