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tively limited, and will include the Acacia, Lime, Lemou, Orange, 

 Quince, Pomegranate, and Walnut. Some few other trees might be 

 added, and it is particularly partial to the Rose and tlie Nettle ; but it 

 is doubtful whether the species could permanently thrive and multiply 

 to an injurious extent on many other trees than those mentioned. 



'^AU young scale insects are quite active when they first hatch, and 

 most ot them at this time are extremely small, and when very thick 

 upon a tree, instinctively, or at least very easily, drop from the termi- 

 nal twigs and branches. Their specific gravity at this time is so slight 

 that they are easily wafted with the wind in their descent. This general 

 truth a|)plies with equal force to the Icerya, which is readilj'^ carried 

 from tree to tree and irom orchard to orchard by the agency of wind, 

 by running water, or by birds or other insects. Another local means 

 of transport not to be ignored is upon the clothing of persons engaged 

 in cultivating, upon packages, and upon all implements used, whether 

 in cultivating or harvesting the crop. This particular species also has 

 quite a habit of crawling over the ground, and its local spread is very 

 materially enhanced thereby. 



"It is carried longdistances,however,chiefly by high winds, birds, and 

 commerce, and its introduction from one continent to another has' un- 

 doubtedly been effected by the latter method upon young trees or 

 cuttings." * 



More light, however, is yet needed upon the question of the original 

 habitat of the species, and as the settlement of the question is impor- 

 tant in many respects I have during the past year been endeavoring to 

 get definite information upon the subject. Without going into techni- 

 cal details, which would not interest you, I maj^ briefly state that the 

 question arose in my mind a year ago as to the probable identity of 

 Icerya purchasi and I. sacchari, which last came from the islands of Mau- 

 ritius and Bourbon, and which is injurious to Sugar-cane there. On the 

 supposition that the two described forms were specifically identical, 

 light is at once thrown upon its wide distribution. It occurred to me 

 that an insect which affected the sugar-cane could be easily transported 

 from the sugar-producing islands in the Indian Ocean to Australia, 

 South Africa, and California, either consecutively one from the other, 

 or to either or all directly, through the sugar trade, especially when it is 

 known that in many cases in packing the coarser sugars it is the custom 

 to put pieces of cane in the packages to facilitate drainage. I took some 

 pains, therefore, to first decide by an examination of si)ecimens whether 

 purchasi was really distinct from sacchari or not, and this could only be 

 done conclusively by examination of the types. My old friend, Dr. Sig- 

 noret, who is the leading French authority on the Coccidte, was unfort- 

 unately very ill at his country home when I was in Paris, last October, 

 but he kindly sent his keys and permitted me to examine his collection 



* From an address by the writer before the State Board of Horticulture at Kiver- 

 side, Cal., April?, 1887. 



