492 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



high power of microscope, near the anterior lateral border of each abdominal segment 

 except the last two. Meso- and meta-thoracic segments (second and third) without 

 spiracles. Prothorax with a spiracle somewhat larger than those upon the abdomen, 

 situated on each side near the posterior margin. 



Larval Life-History. — It is very difficult to gather data on these 

 interesting sap feeders because the larvae if removed from their mines 

 are unable to reenter the bark to continue mining and therefore soon 

 die. On hatching, the young larvae, without exposing themselves, 

 immediately enter the twig and begin their mines which extend partly 

 around the twig before running lengthwise. They molt twice before 

 winter sets in and hibernate as third instar larvae in their mines, pro- 

 tected from severe climatic changes only by the dead bark covering 

 the tunnel. With the coming of warm days in the spring they resume 

 activity and molt a third time about the middle of May. During June 

 the fourth instar mining larvae become full grown. 



Hypermetamorphism. — In this species all the mining larval stages 

 are flat, legless, with exserted mandibles fitted only for separating the 

 tissues of plants and not for masticating purposes. In structure all 

 these stages are alike excepting in the proportionate size of the thorax 

 and abdomen. In the young larvae the head and thorax are much 

 wider in proportion to the abdomen than in later stages. 



Upon reaching maturity the mining larva retreats a short distance 

 and remains quiescent at one side of its mine. During this quiescent 

 period the larval skin remains intact while internally a hypermeta- 

 morphic stage is formed, called the intermediate or pseudo-pupal stage. 

 The head of the intermediate stage is formed within that of the mining 

 larva and gradually contracts until the outline of both are readily 

 seen under the microscope. In the meantime the body has gradually 

 become shorter and more cylindrical. The formation of this inter- 

 mediate stage has been excellently discussed by Rev. J. J. DeGryse 

 {Proc. Ent. Soc. Wash., vol. 18, p. 164, 1916) who observed this phe- 

 nomenon in Marmara fulgidella Clemens. 



Within the pseudo-pupal stage is formed the true spinning larva 

 or pre-pupa, and when complete it emerges, casting both the inter- 

 mediate and mining larval skins at the same time. This is accom- 

 phshed by forcing its head backward and breaking the skin of both 

 preceding stages transversely at the first abdominal segment. The 

 head and thorax are first liberated, followed immediately by 

 emergence from the abdominal exuviae. 



Spinning Larva or Pre-Pupa (Fig. 24, 2): 



Length 5 mm. Color yellowish-brown with tinge of red. Body shorter, more 

 cylindrical, and incisions between segments less pronounced than in mining larva. 



Head smaller and more typically lepidopterous than in previous stages (Fig. 24, 6). 

 Chitinous supports reduced in number. Mouthparts markedly different from mining 



