59 



Psi, absent altogether from tridens; anJ, indulging benignantly in improving plati- 

 tudes about general principles, affinity and analogy, extended range of observations, 

 and so forth, would probably leave the bewildered lepidopterist under the idea that 

 there was something, some unknowu property, in Science that entirely superseded 

 truth and fact, and that was far beyond the reach of his limited capacity. To go a 

 step further, if the lepidopterist pertinaciously adhered to the truth, and exhibited the 

 perfect insects of Psi and tridens, then the entomologist would infallibly turn on his 

 heel, 'more in sorrow than in anger,' and leave the lepidopterist in his error, con- 

 vinced that it was useless to argue with one whose ignorance was so 'crass.' In all 

 this the lepidopterist is right; he has assiduously worked mines of knowledge, the very 

 existence of which are unknown to the entomologist. Even in our British Lepidoptera 

 there are numbers of pairs which require the most highly educated eye to separate them 

 correctly. Let the inquiry be instituted ; and from this inquiry must be eliminated 

 in toto all questionable species, all instances of abnormal form and colour ; all sea- 

 sonal, climatal,altitudinal, latitudinal, geographical, geological or other acknowledged 

 sources of variation ; all second generations in the same year : those natural witnesses 

 only should be examined which, living on the same spots, at the same time, and under 

 the same conditions, originate from different eggs, differ totally in the larva, and ap- 

 proach almost to identity in the imago. I think it is absolutely impossible to exa- 

 mine a rich collection of British Lepidoptera without being struck with the constant 

 recurrence of such pairs. I will cite a few examples- 



Argynnis Adippe and A. Aglaia Tasniocampa Populeti and T. instabilis 



Argynnis Selene and A. Euphrosyne Olaea Vaccinii and G. spadicea 



Sesia bombyliformis and S. fuciformis Dianthecia capsincola and D. Cucubali 



Anthrocera Lunicerag and A. Trifulii Xylina petrificata and X. semibrunnea 



Procris Statices and P. Globularis Calocampa exoleta and C. vetnsla 



Lithosia complana and L. complanula Cucullia Scrophularia) and C. Lychnitis 



Porthesia auriflua and P. chrysorrhoea Catocala proraissa and C. sponsa 



Clisiocampa neustaia and C. castveusis Brephos Parthenias and B. notha 



Notodonta dicla?a and N. dictaioides Tephrosia crepuscularia and T. laricaria 



Acronycta Psi and A. tridens Ypsipetes ruberaria and Y. iinpluviaria 



Caradrina blanda and C. Alsines Cheimatobia dilutaria and C. autumnaria 



I have a list of seventy-four other pairs ; but these are sufficient for my purpose, and 

 I think it will be difficult to explain away their teaching. I have already antici])ated 

 some objections: I will allude to others. It is said, in the instance of Psi and tridens, 

 that on the North-American continent four, that is two pairs, of Acronyctae exist which 

 approach our British ones so closely that a complete series is thus established ; there 

 is also a solitary European species, cuspis, which seems to be allied to all the others. 

 These facts do not appear to me to militate against the view I have taken of the pre- 

 valence of pairs : perhaps one of the North-American pairs may be identical with our 

 Psi and tridens, and the other pair qui|B distinct ; but I learn that no pains have been 

 yet taken to distinguish the larvae of these species: the continental cuspis standing 

 somewhat isolated is no objection, as I do not say that all species are associated in 

 pairs, but only that some are so. Again, I cannot admit the doctrine of chance, that 

 the correspondence between two species is a mere matter of accident. Finally, to 

 the question of the general entomologist, ' Are these pairs really composed of two 



