618 



AN INTRODUCTION TO ENTOMOLOGY 



Fig. 757. — Wings of Gracilaria. (After Spuler.) 



antennge are long; the scape forms an eye-cap in some species and 

 not in others. The fore wings are lanceolate, normal or with some- 

 what reduced vena- 

 tion (Fig. 757) ; usu- 

 ally without an ac- 

 cessory cell, but 

 sometimes one is 

 pi-esent in the genus 

 Far or nix. i li-j nnid 

 wings are lanceolate 

 or linear; in many 

 members of the 

 family they are ex- 

 panded near the 

 base, formingamore 

 or less prominent 

 hump in the costal 

 margin, and in 

 some species vein Ri is free, not coalesced with vein Sc. 



The adult moths when at rest elevate the front part of the body, 

 the fore legs being held vertically so that the tips of the wings touch 

 the surface on which the insect rests. 



The larvas are extraordinary; when young they are very much 

 flattened and have thin, blade-like mandibles and vestigial maxillse 

 and labium ; they merely slash open the cells of the leaf and suck up 

 the cell-sap ; later they usually have normal mouth-parts and eat the 

 parench}Tna. The young larvs always make a flat blotch mine; 

 later they make a blotch mine in which the epidermis of one side of 

 the leaf is thrown into a fold by the growth of the leaf, i. e., a tenti- 

 formmine, or they roll a leaf. The larvse have only fourteen legs or 

 none, never any on the sixth segment of the abdomen. 



This is a large f amly ; about two hundred North American species 

 have been described, and doubtless many more are to be discovered. 



About one-half of our described species belong to the genus which 

 is commonly known as Lithocolletis, but which is termed Phyllonoryc- 

 ter by those who recognize the names in the "Tentamen" of Hubner. 

 The following species will serve as an example of this genus. 



The white-blotch oak-leaf miner, Phyllonorycter hamadryadella. — 

 This little miner infests the leaves of many different species of oaks, 

 and is very common throughout the Atlantic States. The mine is a 

 whitish blotch mine in the upper side of the leaf, and contains a single 

 larva; but often a single leaf contains many of these mines (Fig. 758^ 

 Theyoimg larva is remarkable in resembling more the larva of a beef,:^ 

 than the ordinary type of lepidopterous larvas (Fig. 758, b). It is 

 nearly flat; the first thoracic segment is much larger than any of the 

 others; the body tapers towards the hind end; and there are only the 

 faintest ruaiments of legs discernible. The larvas molt seven times. 

 At the seventh molt the form of the body undergoes a striking change. 



