206 ENTOMOLOGICAL SOCIETY 



Psilocorsis quercicella Clemens. 



X)ne type, Clemens' No. no; alar exp., 13 mm. 



I have bred a very large series, at different times, of what is 

 indisputablv this species, from larvae on oak. These specimens 

 agree with Clemens' description and also with his type. 



There is another very similar and equally common species, the 

 larva of which also feeds on oak and occurs at the same time and 

 same localities as quercicella. The imagoes of this species are 

 exceedingly difficult to separate from quercicella. They are gen 

 erally slightly larger (i to 2 mm. additional expanse) and have 

 the short black transverse lines less pronounced than in this species. 

 They have the apical edge of the fore wing generally more dis 

 tinctly blackish than it is in quercicella. The larvae are quite 

 different from the easily recognized larvae of quercicella , with 

 which they are often found, even between the same two leaves. 

 These larvae are white, with blackish brown head and slightly 

 lighter brown thoracic shield, divided in the center by a straight 

 longitudinal white line ; the second thoracic segment is somewhat 

 reddish laterally ; the rest of the body is white, turning slightly 

 rose-colored at maturity. In the larvae of quercicella the three 

 thoracic segments are black. This species, I am inclined to be 

 lieve, is Zeller's Cryptolcchia obsoletella* with the description 

 of which it agrees well. 



Lord Walsingham made the following species synonymous 

 with quercicella Clemens: (i) Depressaria, cryptolechiella 

 Chambers, f the food plant of which according to Chambers is 

 holly; (2) Hagno faginella Chambers, \ the larva of which 

 feeds on beech : (3) Cryptolechia cressonella Chambers, which 

 I believe with Chambers is the same as Zeller's erroneous con 

 ception of quercicella; (4) Psilocorsis dubitatella Zeller.|| 

 Finally Lord Walsingham identified^" a species bred from Am 

 brosia as this same species. It is evident, as Lord Walsingham 

 himself conceded,** that there is some mistake here. Zeller's 

 conception of Psilocorsis quercicella Clemens, was clearly 

 erroneous, as is shown by the measurement he gives of his speci 

 men (length of fore wing 4'") , which would give an alar expanse 

 of 19 mm. Psilocorsis quercicella varies only slightly in size, 

 and the very largest specimen in a series of more than fifty has 

 an expanse of only 15 mm., while the average size is a little 

 more than 13 mm. 



Zeller, probably, had before him the very similar but larger 



"Verb. k. k. zool.-bot. Gesell. Wien, xxiii, p. 242, 1873. 



t Can. Ent., iv, p. 91, 1873. 



J'Can. Ent., iv, p. 131, 1873. 



Bull. U. S. Geol. Surv. Terr., iv, p. 86, 1878. 



|! Hor. Soc. Ent. Ross., xiii, p. 262, 1887. 



fins. Life, ii, p. 151, 1890. 



** Ins. Life, ii, p. 151, 1890. 



