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Psyche 
[June 
The function of the Dufour’s gland secretion in P. pallidus is 
completely unknown. This gland is highly developed in this ant 
(Fig. i) and contains at least as much material as the poison vesicle. 
The fact that this pseudomyrmicine species had a turgid Dufour’s 
gland even after the poison vesicle had collapsed after secretion of 
the venom strongly indicates that the contents of Dufour’s gland are 
secreted independently of the poison gland. In P. pallidus the Du- 
four’s gland secretion is chemically very distinct from that of the 
poison gland. The fluid in Dufour’s gland is a neutral non-protein 
which because of its high viscosity, is probably quite high boiling. In 
contrast, the poison gland contents consist of basic proteins which 
may not even be miscible with the secretion from Dufour’s gland. 
Wilson (1959) has demonstrated that in the myrmicine Solenopsis 
saevissima Dufour’s gland produces the trail laying substance in this 
species. Callahan et al. (1959) demonstrated that the contents of 
Dufour’s gland could be secreted independently of that of the poison 
glands. However, P. pallidus does not lay trails and indeed smears 
from Dufour’s gland elicited no obvious responses from workers in 
a laboratory colony. Thus with the exception of the genus Solenopsis , 
the function of the Dufour’s gland secretion in the Formicidae remains 
to be determined. 
References Cited 
Blum, M. S. and P. S. Callahan. 
1960. Chemical and biographical properties of the venom of the imported 
fire ant ( Solenopsis saevissima var. richteri Forel) and the isola- 
tion of the insecticidal component. XI Int. Kongr. Ent., Vienna. 
3:290-293. 
Blum, M. S., J. R. Walker, P. S. Callahan and A. F. Novak. 
1958. Chemical, insecticidal, and antibiotic properties of fire ant venom. 
Science 128:306-307. 
Brown, W. L. 
1954. Remarks on the internal phylogeny and subfamily classification of 
the family Formicidae. Insects Soc. 1:22-31. 
Callahan, P. S., M. S. Blum and J. R. Walker. 
1959. Morphology and histology of the poison glands and sting of the 
imported fire ant ( Solenopsis saevissima v. richteri Forel). Ann. 
Ent. Soc. America 52:573-590. 
Wilson, E. O. 
1959. Source and possible nature of the odour trail of fire ants. Science 
129:643-644. 
