Sk. Robson et Jfa. Traniello, RESOURCE ASSESSMENT, RECRUITMENT BEHAVIOR, AND ORGANIZATION OF COOPERATIVE PREY RETRIEVAL IN THE ANT FORMICA-SCHAUFUSSI (HYMENOPTERA, FORMICIDAE), Journal of insect behavior, 11(1), 1998, pp. 1-22
Foragers of the ant Formica schaufussi recruit nestmates to large anth
ropod prey and cooperatively transport the prey to the nest. The size
of the group of ants retrieving prey is significantly correlated with
the prey mass at the point at which the retrieval group reaches the ne
st entrance. To understand the mechanism involved in this ''size match
ing'' process, the regulation of retrieval group size was investigated
by examining the modulatory role of trail pheromones in recruitment c
ommunication and the behavioral processes that might adjust retrieval
group size to prey mass. Laboratory studies of hindgut, poison, and Du
four's gland extracts showed that the contents of the hindgut, which w
as determined to be the source of trail pheromone, induced recruitment
and orientation behavior in ants and regulated the recruitment respon
se of ants in the absence of any other communication signal. However,
chemical mass communication alone did not appear to explain the regula
tion of retrieval group size. Scout ants assess whether to collect pre
y individually or recruit nestmates to group-retrieve 100-, 200-, or 4
00-mg prey but did not vary group size in relation to either the prey
mass or the presence of interspecific competitors once the decision to
initiate group retrieval was made, The number of recruits leaving the
nest was independent of these factors and first matched prey mass dur
ing prey transport, possibly through a process of differential individ
ual response to immobile versus mobile prey items. Unpredictable facto
rs such as prey resistance to movement and rapidly changing degrees of
interspecific competition may preclude scouts from fine-tuning the re
trieval group size before it reaches the prey.