RESOURCE-ALLOCATION, BROOD PRODUCTION AND CANNIBALISM DURING COLONY FOUNDING IN THE FIRE ANT, SOLENOPSIS-INVICTA

The colony founding characteristics of newly mated fire ant queens fro m monogyne colonies were studied in the field and in the laboratory un der haplo- and pleometrotic conditions. Initial queen weight (live) wa s not correlated with subsequent progeny production. During founding, queens lost a mean of 54% of their lean weight, 73% of their fat weigh t and 67% of their energy content. The percentage of fat decreased fro m 44% to 33%. Queens lost weight or energy in relation to the amount o f progeny they produced (Figs. 1, 2). The efficiency of the conversion of queen to progeny increased as more progeny were produced, leading to a decline in the unit cost of progeny (Fig. 3). The more minims a q ueen produced, the lower the mean weight of these minims and the faste r they developed (Fig. 4). In a field experiment on pleometrotic found ing, total brood increased with queen number, peaked between four and seven queens and declined with 10 queens (Fig. 5). Brood developed fas ter at the sunny, warmer site, but total production and queen survival was higher at the shady site. As queen density increased, production per queen decreased as a negative exponential in which the exponent es timated sensitivity of brood production to queen-crowding and the cons tant estimated the production by solo queens (Fig. 9). These effects o f queen number were confirmed in laboratory experiments. The decrease of production per queen was small and not always detectable during the egg-laying phase, but brood attrition was always strong during the la rval period and increased with queen number (Figs. 8, 10). While airbo rne factors may have contributed to this inhibition, most of the brood reduction was due to other causes, probably cannibalism. For a given number of minims, increased queen number increased the mean weight of these minims, an effect that resulted both from a lower minim producti on per queen and from cannibalism of dead queens by survivors (Fig. 11 ). Cannibal queens lost much less weight to produce a given number of minims than unfed control queens, and these minims were heavier (Fig. 12).