LEPIDOPTERA OF NEW YORK AND NEIGHBORING STATES 187 



Group I 



The larva of the first group is cylindrical or subcylindrical in form, and has, 

 beside the thoracic legs, four pairs of prolegs, on segments 7, 8, 9, and 13. It is 

 usually of a pale . greenish or yellowish color. 



The mine may be placed on either the upper or lower surface; but in either 

 case, the loosened epidermis is lined with silk, causing it to contract, and thus 

 producing a roomy, tent-like mine. The mine is at first narrow and somewhat 

 winding, but soon spreads out into a blotch, which sometimes includes the earlier, 

 winding part. The outline of the loosened epidermis represents the final size of 

 the mine, no further increase taking place. The mine may be oval or circular, 

 or, in rare instances, nearly rectangular in shape, sometimes limited by two veins. 

 Usually the larva feeds from the circumference inwardly; sometimes it begins 

 at one end and sometimes it feeds irregularly in spots. 



With the exception of ostensackenella, which leaves the mine to pupate, the 

 pupa is formed within the mine, and may or may not be enclosed in a cocoon. 

 When not in a cocoon, it is usually suspended in the mine by a thin meshwork of 

 silken threads. When a cocoon is present, several varieties may be distinguished. 

 The cocoon may be rather small, ovoid, formed of frass and silk; or large, loosely 

 woven, semitransparent, occupying sometimes nearly one-half the mine; or an 

 oval ring with outlines formed of frass. 



The fore wings of the imagoes are usually of some shade of yellow or brown, 

 sometimes, however, with the basal two-thirds almost pure shining white. Upon 

 this yellowish ground color, the more or less white markings appear. The trans- 

 verse markings consist of costal and dorsal streaks, usually curved and oblique, 

 and slightly curved or angulated fasciae, or combinations of these. These streaks, 

 or fasciae, are usually margined with darker scales toward the base; the internal 

 margins of some of the streaks are sometimes lacking. In a few species, some 

 or all of the streaks, or fasciae, may be more or less margined externally also; 

 but in no case is the external margin heavier than the internal one, or is an 

 external margin present, when the internal one is absent. Longitudinal markings, 

 when present, consist of a median streak from the base, sometimes accompanied 

 by streaks along the costal and dorsal margins. The apex sometimes contains 

 a well-defined, regularly shaped, black dot, formed of closely overlapping scales. 

 In other, species, these scales are more or less scattered. The hind wings are 

 unicolorous. 



Key to the species 



A. Ground color of the fore wings pure white, marked with fuscous, irrorated 



bands and bars 2. bataviella. 



AA. Ground color of the fore wings not entirely pure white. 

 B. Fore wings dusted with fuscous scales. 



C. Costal and dorsal streaks large, conspicuous, and curved backward 



26. salicifoliella. 

 CC. Costal and dorsal streaks narrow, straight, forming angulated fasciae 



44. celtifoliella. 

 BB. Fore wings not dusted. 



C. With an apical dot (indistinct in obsoleta) . 

 D. Without a complete median fascia. 



E. One white dorsal streak before the tornus; basal half of wing mostly 



white. 

 F. Three white costal streaks. 



G. Golden basal streak parallel to fold 4. quercialbella 



GG. Golden basal streak parallel and almost contiguous to costa 



for half its length 3. trinotella. 



