June-Oct., 1921 Bulletin of the Brooklyn Entomological Society 75 



CONCERNING SPECIES, WITH NOTES ON PHYTODECTA 

 AFFINIS GYLL. AND PALLIDUS LINN. 



By Howard Notman, Brooklyn, N. Y. 



Any rule whose operation will surely decide whether two forms 

 are to be considered distinct species or not is obviously of the 

 greatest interest and importance to the student of insects. Most 

 pleasing and, superficially at least, exact in this respect is the rule 

 which draws the line between forms and species by the breeding 

 test — that is, that the offspring of any given female must be con- 

 sidered homogeneous. It is curious that this idea should main- 

 tain itself in spite of its evident conflict with the prevailing doc- 

 trines of evolution. Moreover, although apparently exact and 

 final in its operation, closer study shows its effect to be inimical 

 to a careful observation of facts in that it tends to destroy confi- 

 dence in their systematic significance. 



Study of inherited variation seems to have shown conclusively 

 that certain characters called dominant appear in a larger propor- 

 tion of the second generation, where two more or less distinct 

 varieties are crossed. Is it, therefore, altogether impossible that 

 the sexual identity of a species is a dominant character, in which 

 case the corresponding recessive character would be fertile sexual 

 union with closely alHed species? The females produced from 

 such a union might well produce offspring referable to either 

 species. 



The logic of this suggestion would seem beyond criticism. The 

 following facts observed in the field are presented as of interest 

 in connection with it. 



While collecting insects in a meadow at Keene Valley, N. Y., 

 which was partly overgrown with small poplars and willows, the 

 writer's attention was attracted by small reddish, black-spotted 

 chrysomelid beetles which were to be found in numbers on the 

 trees mentioned. Interest was first aroused by the great vari- 

 ability in the marking both on the elytra and the thorax. Fur- 

 ther study showed that, although the beetles found on the two 

 trees were almost identical in form, the thoracic marks of those 

 on the willow were never more than two small black spots, some- 



