5524 Entomological Society. 



can only appeal to the lepidopterist : the general (another term for the superficial) 

 entomologist cannot comprehend my drift. Let a lepidopterist open his breeding- 

 cages, and exhibit to a general entomologist the larvae of Acronycta Psi and A. tridens 

 (to him ' familiar as household words'), of Calocampa vetusta and C. exoleta ; and 

 let the lepidopterist tell the entomologist that these four larva? produce two pairs of 

 moths, of which the individuals composing each pair are so similar that he (the ento- 

 mologist), with all his knowledge, with all his book-learning, could not distinguish 

 between them ; that it required the utmost subtlety in the eye of the lepidopterist 

 himself to distinguish them, and defied the powers of his pen to differentiate them : 

 the entomologist would simply exhort the lepidopterist to greater care in his observa- 

 tions, and caution him against adopting theories which could not be supported by an 

 appeal to Nature; the entomologist, in the most friendly spirit, would point out the 

 differences of form and structure in the larvae ; would probably select Psi and tridens ; 

 would call the lepidopterist's particular attention to the dorsal column on the larva of 

 Psi, absent altogether from tridens ; and, 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 there was something, some unknown property, in Science that entirely superseded 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 pai»:s 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 Glaea Vaccinii and G. spadicea 



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

 Anthrocera Lonicerse and A. Trifolii Xylina petrificata and X. semibrunnea 



Procris Statices and P. Globularias Calocampa exoleta and C. vetusta 



Lithosia complana and L. complanula Cucullia Scrophularise and C. Lychnitis 

 Porlhesia auriflua and P. chrysorrhoea Catocala promissa and C. sponsa 

 Clisiocampa neustria and C. castrensis Brephos Parthenias and B. notha 

 Notodonta dicta*a and N. dictoeoides Tephrosia crepuscularia and T. laricaria 



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



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



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



