The various other families of aculeate Hymenoptera are doubtless more abundant than the species recorded indicate, and it may be safely reckoned that the parasitic Hymenoptera in Ceylon far exceed one thousand species in number, though they are yet only known by means of about two dozen kinds collected at Kandy by Mr. Thwaites.
"Sketches of the Natural History of Ceylon"
J. Emerson Tennent
But the most curious case, shewing on what complex and easily-overlooked relations, so trifling a character as a difference in size between the sexes may depend, is that of the aculeate Hymenoptera; for Mr. F. Smith informs me that throughout nearly the whole of this large group the males, in accordance with the general rule, are smaller than the females and emerge about a week before them; but amongst the Bees, the males of Apis mellifica, Anthidium manicatum and Anthophora acervorum, and amongst the Fossores, the males of the Methoca ichneumonides, are larger than the females.
"The Descent of Man and Selection in Relation to Sex, Vol. I (1st edition)"
Charles Darwin