3 o6 POPULAR SCIENCE MONTHLY. 



THE DISCOYEEY OF THE NATIVE HOME OF THE SAN 

 JOSE SCALE IN EASTERN CHINA AND THE IM- 

 PORTATION OF ITS NATURAL ENEMY. 



BY C. L. MARLATT, 

 U. S. DEPARTMENT OK AGRICULTURE. 



r I THE insect which has had the greatest international importance 

 -*- and has been the subject of more interstate and foreign legis- 

 lation than all the other insect enemies of plants together is a Chinese 

 bark-louse of deciduous trees, known from its first point of coloniza- 

 tion in America as the San Jose scale. This insect has been so thor- 

 oughly exploited in the publications, scientific and popular, in this 

 country, and in horticultural and agricultural journals, that a general 

 account of it is not necessary. It was first discovered in San Jose, 

 Cal., in the grounds of Mr. James Lick, in the early seventies. It soon 

 spread throughout California and the Pacific coast and became the 

 most notable enemy of such fruits as the pear, apple, peach, prune and 

 certain small fruits. Its name of perniciosus was given it by Professor 

 Comstock, who studied it in California in 1880 and reported it to be 

 the most destructive scale enemy of fruits known to him. It has more 

 than maintained its reputation in this regard since that time. 



Up to 1893 it was only known on the Pacific coast, but in that year 

 it was discovered in a small orchard in Yirginia, and the investigation 

 which followed developed the fact that it had got into some large 

 eastern nurseries a number of years before on plum trees from Cali- 

 fornia, and had been spread from these nurseries unwittingly over 

 much of the southern and eastern states. The damage which soon 

 developed from this scale insect in the orchards of peach, pear and 

 apple of the east aroused very considerable excitement, and the alarm 

 thus caused was transmitted to foreign countries with the result that, 

 beginning with Germany, one after another of the European powers 

 adopted measures probibiting the importation of American plants and 

 fruits, or requiring rigid inspection before such admission. Canada 

 adopted similar restrictions, and even such remote countries as the 

 Cape of Good Hope, New Zealand and Java followed suit. Within 

 the different states of the union also various prohibitions on traffic in 

 nursery stock and plants were put in operation. Since 1893 this scale 

 insect has steadily extended its range in the United States and also 

 in Canada, where it soon gained foothold, and it now occurs in prac- 

 tically all the important fruit districts of North America. It lias not 



