LIFE-HISTORY OF THE ARMORED SCALES. 



15 



DIASPINJE. 



(THE ARMORED SCALES.) 



[Plate III, and Figures 1 and 2.]* 



LIFE-HISTORY OF THE ARMORED SCALES. 



The larva. When the young Bark-louse first makes its appearance 

 from beneath the protecting scale of its mother, it is a minute, oval, 

 flattened creature, provided with all the organs usually possessed by 

 the young of insects; namely, six legs, a pair of antennae in front and 



FIG. 1. 



FIG. 1. 1, egg natural size, scarcely T foj inch; 2, larva as it appears when running over the twigs 

 natural length, -fa inch ; 3, its appearance soon after becoming fixed; 4, appearance of scale after the 

 second plate is formed ; 5, form of louse (ventral view) soon after losing its members; G, form oflonse 

 when full crown; 7, fully formed scales, containing louse, as it appears from the under side, when 

 raised ; 8, highly magnified antenna of the larva by an error eight joints, instead of seven, the cor- 

 rect number, are shown in the drawing. (After Kiley.) 



a pair of bristles behind, simple eyes on the sides of the head, and a 

 short sucking beak. 



At first the young larva moves restlessly 

 about, with a lumbering gait, by no means 

 sluggish, yet markedly less rapid than that 

 of the minute and active mites which are 

 often found in company with it. The object 

 of its wanderings is simply to find a suitable 

 spot upon the bark in which to insert its suck- 

 ing tube or beak. Usually within a few hours 

 after leaving the parent scale the young Bark- 

 louse has become a fixture upon the surface of 

 the plant; the sucking mouth-parts, which 

 consist of a bundle of four slender hairs, grow 

 rapidly until they greatly exceed the body of 

 the insect in length, and, penetrating deeply 

 into the tissues of the plant, can never after- 



FIG. 2. a, terminal joint of the 

 female ; &, spines upon the border ; 

 c, excretory pores ; d, pregnant fe- 

 male ; e, structure ot proboscis, 

 showing four components; /. excre- 

 tory scale, showing successive lay- 

 ers; <7, second, or medial, scale; A, 

 larval, or first scale. ( After Kiley.) 



^Figures 1 and 2 illustrate the mode of growth in Mytllaspis pomorum Bouche", 

 the Oyster-shell Bark-louse of the Apple. They are reproduced from the First and 

 Fifth Missouri Entomological Reports (1868 and 1872), in which the facts essential to 

 a complete knowledge of the life-history of Diaspinous Scale-insects are fully set 

 forth by Prof. C. V, Riley. 



