THE CANADIAN ENTOMOLOGIST. 



loose slones, or between ilie base of the tree and the surrounding soil. 

 When the ground is undisturbed they are rarely found more than an inch 

 below the suiface. Sod furnishes ideal winter quarters for the cocoons. 

 The cocoon is light brownish in colour, broadly oval and moderately 

 arched; it is about 2}^ mm. long by i]^ to 2 mm. wide, and is usually 

 slightly wider at one end. It is surrounded by a thin flange foimed by 

 the closeiy united edges of the two valves of which the cocoon is 

 composed. The cocoons are held in place by a few strands of siik. 

 The time at which the larvœ become mature and construct their cocoons 

 varies considerably with the season. On July 6, 191 1, about one-half the 

 larvge had left the mines; on July 21, 1908, and July 19, 1909, a few 

 larvce were still present in the mines. 



The pupa. — After forming the cocoon the larva apparently does not 

 transform at once; a cocoon opened August 4, 1908, contained a larva. 

 The winter, however, is passed in the pupal stage. On October 10, 1911, 

 the writer opened a number ci freshly gaihticd cocoons and found that 

 all the larvae had transformed to pupœ. 



The pupa is about 2 mm. in length, ovate, pointed behind and 

 somewhat flattened. The ventral suiface is brownish ytUow, the dorsum 

 greenish. The eyes are dark coloured and the orange tuft on the head of 

 the moth shows through the pupal skin. On the dorsum of the abdomen 

 there are six transverse interrupted rows of short brownish spines. On 

 each side of the dorsum there is a longitudinal row of wart-like protuber- 

 ances, each bearing a colourless spine. The anterior spines are very 

 short and they gradually increase in length towards the tip of the body. 

 When about to transform to the adult the pupa works itself partly out of 

 the end of the cocoon, probably by the aid of these spines. The empty 

 pupa skin is left protruding from the cocoon. 



Parasites. — No parasites were observed infesting the plum leaf miner 

 until May 11, 1911, when a cocoon was found containing the larva of a 

 Chalcis-fly. The larva is i 4 mm. long, smooth, whitish in colour and 

 rounded at both ends. On June 2, 191 1, two adults of the parasite were 

 found 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 colour 

 and about i^/^ mm. in length. This species has recently been described 

 as Derostenus sahitaris Crosby. 



