QUEEN NUMBER AND THE PRODUCTION OF SEXUALS IN THE FIRE ANT, SOLENOPSIS-INVICTA (HYMENOPTERA, FORMICIDAE)
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To investigate the possibility of queen control over the production of sexuals in polygyne colonies of the fire ant, Solenopsis invicta, large colonies were divided into polygyne (P) and monogyne (M) or queenless (Q-) halves. Sexual larvae were evident in the M and Q- halves 3 to 4 days after colony division, whereas sexual forms failed to develop in all but one of the 32 P halves examined. Both male and female sexuals were produced in abundance in all M (n=25) and Q- (n=7) halves. Evidently, individuals capable of sexualization are present in colonies with many functional queens but are normally prevented from developing. Electrophoretic and morphometric analyses indicated that both haploid and diploid males were produced in the Q- halves, although diploids far outnumbered haploids. It thus appears that queens exert control over all potential and genetically determined sexuals regardless of sex or ploidy. The timing of the appearance of sexual forms following colony division suggests that queen control may be pheromonally mediated and inhibits the growth of sexuals late in larval development. An experiment in which the queens from M and P halves of colonies were exchanged demonstrated the reversible nature of this inhibition within colonies, but also suggested that once individual larvae develop beyond a critical point they are no longer subject to queen control. Despite seasonal variation in the production of sexuals in the field, no substantial differences between colonies collected in the summer and fall were found in their response to colony manipulations. The interaction of colony weight and number of queens present prior to colony division was associated with the number of males produced in the Q- halves, but no factors examined were associated with the number of females produced in these halves, or with the number of males or females produced in the M halves. 1986 Springer-Verlag.
