1964] 
Blum, Moser , Cordero - — Chemical Releasers 
5 
Based on an examination of the glands associated with the sting in 
the attine genera Cyphomyrmex , Trachymyrmex, Acromyrmex , and 
Atta , it appears that at least some internal morphological characters 
may be quite similar throughout the tribe. In Cyphomyrmex rimosus, 
the most primitive of the attines, (Weber, 1958), the paired free arms 
of the poison gland are rather blunt structures which are enclosed in a 
large bulbous vesicle. The vesicle rapidly narrows down to an ex- 
tremely fine duct which is attached to a very reduced sting. Dufour’s 
gland is inserted near the base of the sting and is considerably smaller 
than the poison glands. Notwithstanding differences in size, the form 
and relative proportions of the poison and Dufour’s glands in Tra- 
chymyrmex, Acromyrmex, and Atta are virtually identical to those 
of Cyphomyrmex. Indeed the sting-associated glands of a minor 
worker of Atta cephalotes are a veritable carbon copy of those found 
in a Cyphomyrmex worker. It thus appears that the gross morphology 
of the poison apparatus of workers in the most primitive attine Cy- 
phomyrmex, has undergone little change during the evolution of this 
tribe. The gross form of the glands associated with the reduced sting 
form a distinctive attine structure which may be an excellent diagnos- 
tic character for this tribe. 
The lack of generic specificity of the odor trail substances of the 
four attines must be regarded as further evidence for the close rela- 
tionship of the attine genera. In spite of the fact that Cyphomyrmex 
and Atta stand at the phylogenetic extremes of the tribe Attini, the 
odor trail substance of Cyphomyrmex is capable of releasing trail 
following behavior in A tta and vice versa. It is interesting to contrast 
the lack of generic specificity in the attine odor trail substances with 
the great specificity of the odor trail substances in the myrmicine 
genus Solenopsis. In transposition experiments with species of 
Solenopsis, Wilson (1962) demonstrated the odor trail substances of 
three members of this genus were highly species-specific. In addition, 
the Solenopsis trail substances produced no trail following in four 
other myrmicine genera. Similarly, the odor trail substances of the 
Attini do not produce any response in any of the myrmicine genera 
that we tested. One possible explanation that is consistent with the 
lack of specificity of the trail substances among the attines is that 
the odor trail chemicals are identical or closely related in the different 
genera. If this is correct, then the biogenetic pathway for the synthesis 
of the odor trail compound (s) in Cyphomyrmex has been utilized by 
the more highly developed attine genera with little modification. It 
is thus possible that the Attini are closely linked by the natural prod- 
ucts chemistry of their poison glands. 
