Occurrence of 'empty' spermathecae in spring queens of Bombus terrestris L.
During a trial on indoor mating between Bombus terrestris adults from colonies reared in the laboratory (Danish Research Service for Plant and Soil Science, Bee Division) the spermathecal content was investigated in queens that had dug themselves into the sphagnum at the bottom of the mating boxes. Ten queens were dissected, and two had no semen in their spermathecae. Total 61 59 2 (3%) before the first importation (1990) of bumble bee colonies for pollination tasks, the 61 investigated queens represent the natural spring populations. The occurrence of spring queens without semen in the spermathecae might explain why some spring queens during domestication can be induced only to rear male (haploid) progeny. It is well known that queen bumble bees can invade established colonies and kill and replace the founding queen. It is however not known if semenless Bombus queens can do this, and it is unknown whether they are able to develop eggs; if they do, they might change the genetics as well as the proportion of males produced in the colonies. The occurrence and behaviour of semenless queen bumble bees ought to be investigated further, and their possible role should be taken into account when working out models of genetic strategies in bumble bee species.