The Plum Leaf-miner 223 



in a vial containing cocoons of the moth. They had emerged through 

 a smooth round hole in the side of the cocoon. In the fall of 191 1 the 

 parasites had increased in numbers so that nearly one half of the cocoons 

 examined were infested. So far only three adults, all males, have been 

 reared. They are small, four-winged flies, metallic green in color and 

 about 1 1 mm. in length. This species has recently been described as 

 Derostenus salutaris (Can. Ent., XLIII, p. 414). 



Technical description. — Derostenus salutaris Crosby. (Fig. 38.) Male. 

 Length i^ mm. Head, thorax, and abdomen bright metallic green, 

 the latter darker and bluish in certain lights. Head viewed from 

 above strongly convergent behind the eyes and strongly concave poste- 

 riorly ; the occiput bounded by a distinct ridge bearing a row of blackish 

 hairs. Viewed from in front the inner margin of the eyes sinuate. An- 

 tennae inserted near the mouth and separated by a distinct median carina. 

 Head finely shingled and clothed with sparse short dark-colored hairs. 

 Eyes finely pubescent. 



Thorax more distinctly shingled and clothed with a few rather long 

 brownish hairs. Propodeum with a median carina and a transverse 

 carina before the apex; no lateral carina present. 



Antennae dark, nearly black; scape white; ring-joint distinct; funicle 

 of three nearly equal segments; club ovate, of three closely united seg- 

 ments, the last small and style-like; flagellum filiform. Legs white; 

 coxae metallic green. Wings hyaline, postmarginal vein about as 

 long as the stigmal. Petiole of abdomen a little longer than hind coxse, 

 finely and densely punctate. 



Abdomen viewed from above nearly circular, smooth and flattened. 

 The first segment back of petiole about one third length of the abdomen, 

 the others subequal. 



RELATED SPECIES 



The genus Nepticula, to which the plum leaf -miner belongs, contains 

 over 40 species from the United States, while in the British Isles, where 

 entomologists have given more attention to these minute moths, over 70 

 species are known. The larvae of all species of this genus so far as known 

 are leaf -miners, feeding within the leaf just below the upper epidermis. 

 As a rule each species is confined to a particular food plant, or at most 

 to two or three closely related food plants. 



The following list gives the food plants of the American species of 

 Nepticula as far as known: 



N. amelanchierella Clemens. Juneberry (Amelanchier canadensis). 



N. anguinella Clemens. Oak. 



N. castanecefoliella Chambers. Chestnut, white oak, chestnut oak. 



N. carycefoliella Clemens. Hickory. 



