208 



EXPERIMENTAL FARMS. 



Fig. 



Life History. — The winter 

 is passed by the partially 

 grown insects beneath their 

 scales. With the return of 

 •warm weather the next spring, 

 growth is resumed, and the 

 males reach maturity a few 

 days before the females. They 

 are extremely small two- 

 winged flies (Fig. 17) and 

 when examined under a mas- 

 nifying glass are found to 

 have orange yellow bodies, 

 iridescent dusky wings and 

 black eyes. These minute 

 creatures have no mouths, so 

 can take no food; consequently 

 after having fertilized the fe- 

 males they very soon die. 

 The date when the females 

 and begin 



become full-grown 



17. — San Jose Scale, male — much enlarged. The natural size is 

 shown by the line in the circle below the right wing. 



to produce young varies with locality and climate. In Arizona the young larvae 



are recorded as appearing in March. At Washington it is by the middle of May ; in 



New Jersey during the last days of May; in the state of New York, early in June. At 



Amherst, Mass., they were first noticed 12th June, and, as far as I can learn, in our 



Niagara district between the middle of June and 1st of July. Most careful observations 



have been made under direction of the United States Entomologist, by Mr. Theo. Pergande. 



The following condensed life-history is compiled chiefly from United States Division of 



Entomology, Bulletin No. 3, N'.S., in which Mr. Pergande's observations are recorded. 



The adult female gives birth to living young, instead of laying eggs like most other 

 scale insects. Ordinarily, as with the Oyster-shell Bark-louse, eggs laid beneath the 

 scales, in the course of a longer or shorter time, hatch, and the young larvae migrate to 

 different parts of the plant ; but in the case of the San Jos^ Scale living young are pro- 

 duced day and night for a period of nearly six weeks before the exhausted female 

 perishes, and this at the rate of about nine or ten every twenty-four hours. After birth, 

 the young larva remains motionless for a short time beneath the scale of the mother, it 

 then forces its way out and runs over the plant, seeking a suitable place to settle. It is a 

 microscopic oreature, pale orange in colour with an oval body, six legs and two feelers. 

 The long thread-like proboscis, with which it sucks the sap of the plant, is doubled on 

 itself and lies in a groove of the body wall. After crawling about for a few hours, the 

 larva settles down and works its bristle-like sucking tube through the bark and remains 

 fixed, if it be a female, for life, and if a male, until fully developed, when it will have a 

 few hours more active life, during which it can fly about. 



The development of the scale begins even before the larva becomes fixed. The 

 secretion of the scale starts in the form of very minute white waxy filaments, which 

 spring from all parts of the body and rapidly become more numerous until, within two 

 days, the insect is entirely concealed by a whitish shell or scale, which has a prominent 

 central nipple. The scale is formed by the matting and melting together of the waxy 

 filaments. As in the development of most insects, there are also with these scale-insects 

 distinct period? of the larval life, divided by moults of the skin, and, in the case of the males, 

 marked by important structural changes. The first moult takes place when the larva 

 is twelve days old. Up to this time, the male and female scales are exactly similar 

 in size, colour and shape ; but after the moult the insects beneath the scales bear no 

 resemblance to each other ; the males are larger than the females and have large purple 

 eyes ; while the females have lost their eyes entirely. The legs and feelers have dis- 

 appeared in both sexes. Eighteen days after birth the second moult occurs and the 

 males chaiige to the first pupal condition (pro-pupa). The male scales now assume an 



