ABDOMINAL TROPHALLAXIS IN THE SLAVE-MAKING 
ANT, HARPAGOXENUS AMERICANUS 
(HYMENOPTERA: FORMICIDAE)* 
Robin J. Stuart 
Department of Zoology, Erindale College, 
University of Toronto, 
Mississauga, Ontario, L5L 1C6 Canada 
Abdominal trophallaxis refers to the passage of fluids from the 
abdominal tip of one individual to the mouthparts of another. It is 
common among lower termites (Kalotermitidae and Rhinotermiti- 
dae) where it functions in the vital transmission of intestinal 
flagellates to newly molted individuals. However, it has rarely been 
documented among ants (Wilson, 1971, 1976). By strict definition, 
the term abdominal trophallaxis should be applied only when 
alimentary fluid is being transmitted (Wilson, 1971). Nevertheless, 
in practice, the origin of the fluid is often unknown, at least initially. 
Indeed, in all cases where this behavior has been described in ants, 
the fluid is either suspected of being, or has since been shown to be, 
ovarian in nature. For example, workers of certain Eciton species 
(Dorylinae) readily feed from droplets secreted from the tip of the 
queen’s abdomen, but this behavior has been observed only during 
egg-laying bouts (Schneirla, 1944; Rettenmeyer, 1963). So-called 
“proctodeal feeding” has also been described among the Doli- 
choderinae ( Dolichoderus quadripunctatus, Tapinoma erraticum 
and Iridomyrmex humilis) (Torossian, 1958, 1959, 1960, 1961). 
However, at least in the case of D. quadripunctatus, the fluid has 
been identified as the yolky remnants of abortive trophic eggs 
(Torossian, 1978, 1979). Among the Myrmicinae, Zacryptocerus 
varians exhibits a similar behavior which is also thought to be 
associated with egg-laying (Wilson, 1976). This paper reports an 
unusual and interesting case of abdominal trophallaxis in colonies 
of the socially parasitic myrmicine ant, Harpagoxenus americanus. I 
have followed Wilson (1976) and tentatively applied the term 
abdominal trophallaxis, because the origin of the fluid is unknown. 
H. americanus is an obligatory slave-maker and forms mixed 
colonies with members of certain Leptothorax species in eastern 
* Manuscript received by the editor November 10, 1981. 
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