106 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 



11. METHODS AND OBSERVATIONS. 

 (a) Systematic Position and Characteristics of Lithocolletis. 

 The genus Lithocolletis belongs to the large family Tineidse of the Micro- 

 lepidoptera. It comprises a large number of very small moths, varying in 

 expanse from 4 to 12 mihimeters. The larvae are exclusively miners, usually in 

 leaves or very rarely in the bark of stems. The entire larval and pupal existence 

 with one or two exceptions is passed within the mine. The genus, as originally 

 estabhshed, has a remarkably uniform structure and a very characteristic 

 appearance, enabling one to recognize the species easily. The structural char- 

 acteristics which distinguish the typical and principal group are the fohowing: 



,^ IP 9 ^ Face smooth; crown tufted; labial palpi por- 



^-^^^^^ rected or drooping, moderately long and pointed; 

 maxillary palpi rudimentary; tongue of moderate 

 ^^.^^^^^^^^^ length; antennae nearly attaining the wing length, 



^^^^^^^^^=^ simple in the male, basal joint thickened and bearing 



FiG.'i. Nen^iionoiLithocoiieUs. ^ P^^.^^^' ^hc forewiugs are elongate, lanceolate, 



acuminate. The hindwings are about one-half the 

 breadth of the forewings, linear lanceolate and fringed with ciha whose length 

 is from four to five times the breadth of the wings. The venation is illustrated 

 by Fig. 1;^ forewings, lb simple, 3 absent, 4 absent, 6 absent, 7 to costa, 8 ab- 

 sent, 11 absent; hindwings, 3 absent, 4 absent, transverse vein absent between 2 

 and 5, 6 absent. The posterior tibiae bear appressed hairs. 



All of the European species and the great majority of the American species 

 conform to the above conception of the genus. There are, however, in North 

 America a few species belonging to two different groups, which differ structurally 

 from the typical species; for these, two subgenera, Porphyrosela 

 and Cremastobomhycia have been erected (Braun, '08). The 

 former of these, Porphyrosela, differs from Lithocolletis in the 

 absence of vein 10 of the forewings, the absence of a pecten on 

 the first joint of the antennae and in the absence of hairs on the 

 hind tibiae.^ It thus represents a later development, phylogen- of porphyrosela 

 etically, in the direction usually taken in this family; that is, 

 a reduction in the number of veins (Fig. 2). Cremastobombycia is of a more 

 ancestral type than the typical Lithocolletis; it possesses an additional vein in 

 each wing; on the forewing, vein 4 is present and stalked with 5; on the hind- 

 wing, vein 6 is present and long stalked with 5 {Fig. 3) . 



In the European fauna, the typical Lithocolletids are a very homogeneous 

 group of species both as regards larval characteristics and imaginal markings. 



1 References in italics are to the text figures, those in Roman type to the figures on the 

 plates. 



2 Since this paper was written, studies on very closely allied species have shown that these 

 characters are not sufficiently constant to define a genus (Meyrick, Genera Insectorum, 128me 

 Fascicule, p. 5, 1912). Vein 10 is probably faintly visible in large specimens of L. desmodiella. 



