62 Inheritance of Mela?iism in Tephrosia (Ectropis) 



true ; but, speaking for myself, and as the outcome of a prolonged study 

 of the relationships existing between various critical species in the 

 Lepidoptera, as well as in other groups, I am not prepared to grant its 

 truth. Either a species is an entity or it is not ; either tangible struc- 

 tural and other fundamental characters — physiological or otherwise — 

 enabling one to differentiate allied forms from one another, exist or they 

 do not. If they do not, then no amount of "judgment" would separate 

 the forms in question so completely that/ one would regard them as 

 more than local'races or phases of the same species. For example, even 

 if not so striking as those by which we distinguish Pieris napi and 

 P. hrassicae, the difference between the two Small Whites, P. napi and 

 P. rapae 18 absolute; "judgment" cannot affect their status in the 

 slightest. 



(2) The specific differentiation q/" Tephrosia (Ectropis) bistortata and 

 T. crepuscularia. 



All of this is very pertinent to the case of Tephrosia bistortata and 

 T. crepuscularia. Undoubtedly, to the untrained mind, they would 

 appear to afford excellent material upon which to exercise one's judg- 

 ment, so closely do they approximate in their superficial characters. 

 The obvious differences — their depth of colour, time of emergence, their 

 univoltine or bivoltine nature, which to the student are quite valueless 

 because possibly (and for the most part actually) based on meteorologi- 

 cal factors — seem to attract the casual worker like a magnet ; upon 

 them he must found his arguments. However, if one probes a little 

 further into the matter than the mere consideration of a row or two of 

 dried imagines in a cabinet with the data on the accompanying labels, 

 one finds that definite structural and physiological differences manifest 

 themselves. Although the divergences are not great, the genitalia in 

 both sexes present significant differences, as will be seen from the 

 figures (Figs. 1 and 2). In particular, attention is drawn to that 

 strange and apparently meaningless dissimilarity in the knobs on the 

 hairs of the cristae of the male apparatus (Fig. 3). Constant differences 

 in colour and pattern, occurring throughout the common range of the 

 two, are recognisable ; the larval markings differ in design ; so, too, the 

 bright green ova of T. crepuscularia are always markedly distinct in 

 cubical content and shape from the yellower ones of the related T. bis- 

 tortata. 



Furthermore, the geographical ranges of the two insects do not 

 coincide ; T. bistortata is Holarctic whereas T. crepuscularia does not 



