The Plum Leaf-miner 221 



"Head and frontal tuft orange, antenna eye-caps and side tufts white; 

 antenna whitish gray; thorax bronzy black; abdomen light gray; legs 

 yellowish white, posterior tarsi finely ringed with black. 



"Forewing. — Bronzy black with a shining white fascia at outer third, 

 cilia and hind wings light gray." 



The egg. — The act of egg-laying has not been observed, but probably 

 it takes place in the evening or at night, as the moths are rarely seen on 

 the leaves during the day. The eggs are attached to the under surface 

 of the leaf, usually at the forks of the more prominent veins. The egg 

 (Fig- 3S) is about 0.3 mm. long by 0.2 mm. wide, oval in outline, flattened 

 where attached to the leaf and domiC-shaped in profile. The green of the 

 leaf shows through the transparent eggshell, making it a difficult object 

 to find. The eggs are most easily located by holding a leaf at an angle 

 in the sun so that the light will strike it obliquely, when they will be seen 

 as minute glistening dots. The exact time required for the hatching of 

 the egg has not been determined, but it cannot be far from two weeks. 

 On June 2, 1908, an examination of the orchard showed that a great 

 number of eggs had been laid; on June 9 no eggs had hatched, and on 

 June 1 8 hatching had just nicely begun. 



The larva. — In hatching, the larva eats its way out of the eggshell on 

 the underside next to the leaf, and enters the leaf directly without coming 

 out on the surface. This is a point of great practical importance, as show- 

 ing the futility of attempting to kill the larvag with an arsenical spray. 

 When full grown the larva is about one sixth inch in length, greenish white 

 in color with the head light brown; the contents of the alimentary canal 

 show through the semitransparent body wall as a greenish or brownish 

 stripe. The larva is legless and only slightly flattened; the constrictions 

 between the segments are rather deep but obtuse; the surface of the body 

 is smooth and clothed with dense, very short, microscopic hairs inter- 

 spersed with a few larger ones. (Fig. 36.) 



The mine. — After entering the leaf directly from the underside of the 

 egg, the young larva eats out a narrow linear burrow, or mine, an inch 

 or less in length, leaving the outer layers of the leaf intact. This part 

 of the mine usually follows a tortuous course but may be nearly straight. 

 The larva next enlarges its mine into an irregular ovate blotch about one 

 half inch in length. In the linear part of the mine the excrement is left 

 as a blackish streak extending along the center of the burrow ; in the blotch 

 mine it forms a broad, irregular band along the center, but does not extend 

 to the tip. The outer leaf layers overlying the mines turn brownish or 

 yellowish; the upper layer seems to be thinner than the lower, and the 

 mines are more conspicuous when viewed from above. There are often 

 ten or a dozen mines in a single leaf. (Figs. 27 and 28.) 



