Reproductive competition involving oophagy in the socially nesting beeXylocopa sulcatipes

Abstract

Several types of nesting associations, termed quasisocial (females more or less identical, no division of labor), semisocial (females of the same generation, with division of labor) and matrifilial (overlap of generations, with division of labor) are described in many primitively social hymenopteran species. In the latter two types, at least one potentially reproductive female forgoes her own reproduction in favor of that of a dominant female. Quasisociality is generally of a temporary nature, because dominance relations develop. It turns then into semisociality [11. The large carpenter bee Xylocopa sulcatipes in southern Israel has been described as forming both solitary and social nests [2, 3]. This paper shows that in certain associative nests founded by two females an extreme example of reproductive competition, oophagy, occurs. A X. sulcatipes egg measures approximately 11 mm in length and 2.2 mm in diameter; for an adult female of 22 mm body length, egg cannibalism therefore represents a significant loss of investment. X. su/catipes typically nests in twigs o f dead branches where the female excavates a straight tunnel. Females also use pre-existing cavities in stems of Arundo, Ferula and other plants existing naturally in the habitat. The female builds a linear array of cells [4]. Each is provisioned with pollen and nectar, and an egg is deposited upon the loaf-like food mass. Finally the cell is sealed with masticated wood. As part of a study on Xylocopa at Hazeva Field Centre, Arava Valley,