LIFE-HISTORY OF THE ARMORED SCALES. 



16 



DIASPIN^. 



(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 antenntie in front and 



Fig. 1. 



Fio. 1. — 1, egg — natural size, scarcely -jhi inch ; 2, larva as il appears wheu running over the twigs — 

 natural length, ^Jj inch ; 3, its appearance soou after becoming fixed: 4, appearance of scale aftei- tlie 

 second plato is formed ; 5, form of louse (veniral view) soon after losing its members; 6. forni of louse 

 when full srown ; 7. fully formed scales, containing louse, as it appeals from the under side, when 

 raised : 8. highly magnitied antenna of the larva — by an error eight joints, instead of seven, the cor- 

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



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 [)arent scale the young Bark- 

 louse has become a fixture ui)on the surface of 

 the plant; the sucking mouth-parts, which 

 (!onsist of a bundle of four slender hairs, grow 



Fig. 2. 



Fig. 2. — a, terminal joint of the 

 female : h, spines upon the border ; 

 c, excrett>rv pores; d, pregnant fo- 



rapidly until they greatly exceed the body of :;^:.':ing-forcompo^,e"ntsf/:Se: 

 the insect in length, and, penetrating deeply ^^f r:^.nK'Ti.:S^:^ It 

 into the tissues of the plant, can never after- lawal, ornrst scale. ( After KUey.) 



"Figures 1 aud 2 illustrate the mode of growth in Mijtilasjns 2)oinorum Bouch^, 

 the Oyster-sheil Bark-lou.se of the Apple. They are reproduced from the First and 

 Fifth Missouri Entomological Report.s (186H and 1872), in which the facts essential to 

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

 forth by Prof. C. V. Riley. . 



