20 



of these diflferent species of armored-scale insects very closely resemble 

 each other, and can not be distinguished without careful microscop- 

 ical study. While very minute, the young are yet visible to the naked 

 eye, and during the breeding season may be seen, b}'^ sharp inspection, 

 running about on the leaves, twigs, and fruit. In color they are 

 usually light lemon-yellow. They have six well-developed legs, also 

 antennas and e3^es, and are highly organized in comparison with the 

 degraded condition soon to be assumed. After linding a suitable sit- 

 uation, often within a few minutes from the time of their emergence, 

 though sometimes not for an hour or two, they settle down, thrust 

 their long slender hair-like beaks into the plant, and immediately 

 begin growth, the first evidence of which is the secretion of waxy 

 filaments from the upper surface of the body, which mat down and 

 form the beginning of the scale covering (fig. 12). This waxy secre- 

 tion continues during the life of the insect, the covering scale being 

 enlarged as the insect increases in size. The females undergo two 

 molts, and the skins thrown off in these molts form a definite part of 

 the scale, being cemented to it closely with the wax. The female 

 insect, after the second molt, soon reaches full size, and when fertil- 

 ized by the male begins to develop her numerous progeny. 



The preliminary stages of the male scale insect exactly correspond 

 with those of the female. After the first molt, however, the male 

 assumes a slightly different appearance, being more elongate than the 

 female at this stage. With the second molt the male diverges entirely 

 from the female; the old skin is thrust out from beneath the covering 

 scale, and does not become a part of it, as with the female, so that in 

 the case of the male insect the first-shed skin only is associated with the 

 scale, which never becomes more than one-half the size of that of the 

 female. With this second molt the male insect transforms to a pre- 

 liminar}^ pupal stage, in which the antennge, legs, and wings are par- 

 tially developed. A third molt occurs with the male insect, resulting 

 in the final pupal stage, which exhibits more fully formed legs and 

 wings than the preceding stage and also the so-called terminal style. 

 A fourth and last molt of the male produces the perfect insect, which 

 escapes from beneath the covering scale and can fly about (fig. 11, e). 



The periods between the moltings vary with different species and 

 with weather conditions. Most of the species, however, reach full 

 growth in from four to six weeks in summer; development is slower 

 in winter. 



The female insect, having once thrust her beak into the tissues of 

 the plant as a larva and begun the secretion of a covering scale, never 

 moves from her position: and, in fact, if she be removed by force is 

 never again able to penetrate the bark with her sucking beak, and soon 

 perishes. The opportunity for the local spread of these insects is, 

 therefore, limited absolutely to the larval stage, as in this respect they 



