368 STATE HORTICULTURAL SOCIETY 



History. — But little is known of the early history of this species. Ac- 

 cording to our best authorities it is undoubtedly of European origin but 

 was introduced ver}' early into this country. It was first described in 

 173S by a Frenchman named Reaumer who found specimens on an elm 

 in his native country. According to Dr. Howard* it was known in this 

 country as early as 1794. 



The earliest account which we have seen relating to the insect in this 

 state was published by Dr. Asa Fitch in 1856 in his first report as State 

 Entomologist (p. 31). Dr. Fitch states that the insect was then known 

 "everywhere throughout the northern states * * * infestmg the 

 orchards to a grievous extent, causing the death of many trees and im- 

 pairing the health and vigor of many more."' The same writer quotes a 

 Wisconsin correspondent who states that the insect was evidently intro- 

 duced into Wisconsin as early as 1840. It is thus shown that the species 

 had a wide distribution in this country at an early date. 



Present distribution. — The oyster-shell bark-louse is known all over the 

 world. It occurs in more or less abundanc€ wherever apples and pears are 

 grown. In the United States it is reported from Maine to California, 

 although it is not so well known in many of the western states as in the 

 east and south. It is widely distributed throughout this state. While 

 we are receiving specimens from new localities every 3'ear, up to the 

 present time specimens have been received from the following counties: 

 Erie, Niagara, Monroe, Wayne, Ontario, Yates, Schuyler, Seneca, Cayuga, 

 Onondaga, Cortland, Jefferson, Lewis, St. Lawrence, Columbia, Kings, 

 Queens and Suffolk. 



Food plants. — The list of food plants for this insect includes a large 

 number of our common trees and shrubs. In the nursery it is especially 

 abundant upon fruit trees, such as apple and pear, but it should be 

 watched for on other stock such as currant, gooseberry, blackberry and 

 raspberry, also on ornamentals such as maple, birch, elm and lilac. 



Descriptions and life history. — The life history of the oyster-shell bark- 

 louse is very similar to that of many other species of scale insects. If 

 an infested tree is examined in the winter the scales will be found to 

 present the appearance shown in Plate I, fig. 1, which is from a photo- 

 graph of an infested apple twig, natural size. It will be observed that 

 although differing in shape, being longer and narrower, the scales bear a 

 slight resemblance to an oyster-shell, hence the name. If one or two of 

 these scales are turned over [Fig. 2] they will be found to be well filled 

 with creamy white eggs. If, however, the eggs are not observed until 

 nearly ready to hatch they will have turned to a dark reddish-brown 

 color. There are usually between forty and fifty although the number 

 may vary greatly. We have found as few as thirty and more than 

 sixtj' under different scales. The shriveled bodj^ of the female scale 

 will be found occupying a portion of the smaller end. The eggs vary in 

 shape as shown at Fig. 3, which is from a photomicrograph showing a 

 number of the eggs greatly enlarged, but in general appearance slightly 

 resemble miniature hen's eggs. They also vary in size, but from a num- 

 ber of measurements we found that an egg of average size would meas- 

 ure about 0.3 mm. by 0.18 mm. 



The eggs remain protected by the scales all winter. In this climate 

 most of them have hatched by the first of June. In some seasons they 



*Year Book U. S. Dept. Agr. 1894, p. 255. 



