ABSTRACT
One of the most striking peculiarities of the various groups of social wasps, social bees and ants surveyed in the preceding lectures is the constant recurrence in all of them of the same general behaviour pattern or motif, with modifications depending on the character of the food and other environmental exigencies. This recurrence, no doubt, is partly due to morphological and ethological similarities among the immediate solitary ancestors of these insects and partly to the more remote common ancestry of all of them. As we have seen, all the social Aculeates are derived from solitary Sphecoids and Vespoids and I have attempted to trace both groups back to hypothetical extinct Bethyloids, the putative primitive stock of the whole Aculeate suborder. The noticeable fact that the social bees, though of Sphecoid ancestry, are nevertheless in many respects more like the social Vespidæ than are the Vespoid Formicidæ, is probably due to the longer and more eventful evolution of the latter.
