49 



CERTAIN METHODS OF JUDGING AND DESCRIBING 

 NE\A^ SPECIES. 



Bv S. Frank Aaron. 



A few papers have appeared in recent numbers of Papilio and else- 

 where, on the subject of true species of Diurnal Lepidoptera. As 

 a citizen of the " Republic of Science" I may venture to add my voice 

 in submission of evidence, which has, it seems to me, been overlooked 

 in this discussion. 



Certain entomologists hold the ojMnion that by observing the charac- 

 ters of lepidopterous larvae they may, with certainty, establish distinct 

 species; that if two forms, appearing as varieties by the characters of 

 the imagines alone, dilTer in the larval characters, they are specifically 

 distinct. Mr. W. H. Edwards, the chief exponent of this doctrine, 

 has expressed himself to this effect: that by breeding he has established 

 distinct species, which by the imaginal characters alone appeared to be 

 mere varieties. 



A work has recently been written by Dr. August Weismann,* con- 

 taining some very interesting experiments on raising Lepidoptera, 

 and it will be found of value to the scientific entomologist. 



Regarding the subject of larval classification, Weismann has shown 

 that the larva and the imago vary in structure independently of each 

 other (vol. ii, p. 401); that the larvae of two very distinct forms may 

 have much resemblance (due to adaptation of similar conditions of life), 

 and, vice versa, that very different larvae may produce the same species 

 (chapter on Phyletic Parallelism of Metamorphic Species). In the 

 summary and conclusion of this chapter he says, ' ' Thus the caterpillar- 

 shaped and maggot-formed larvae of the Hymenoptcra differ from one 

 another to a much greater extent than their imagines, since the latter 

 have experienced a complete transformation of typical parts, while in 

 the caterpillar-formed larvae these parts vary only within moderate limits. 

 Similarly in the case of the Diptera, of which the gnat-like larvre diverge 

 more widely from the grub type than do the gnats from the true flies. 

 On the other hand, the di\'ergence between the imagines of the fleas 

 and gnats is considerably greater than that between their larvae; indeed, 

 the larvae of the fleas would have to be ranked as a family of the sub- 

 order of the gnat-like larvae, if we wished to carry out a larval classifi- 

 cation." (p. 505) Again (p. 506) he says : "The larvae of the fleas, 

 on account of their small divergence from those of the gnats, could 

 only lay claim to the rank of a family, while their imagines are sepa- 



* studies in the Theory of Descent, by Dr. August Weismann, with notes and additions by the 

 author. Translated and edited, with notes, by Raphael Meldola. With a prefatory notice hi,- 

 Charles Darwin, two vols., eight colored plates, London, 1882. 



