224 
Psyche 
[September 
that Stumper (1959) noted in the venom of a member of the 
Formica rufa complex is similarly composed of free amino acids. 
It seems appropriate to ask what role ? if any, free amino acids may 
play in enhancing the toxicity of the highly concentrated formic acid 
in the venom. Ghent (1961) has established that the formic acid 
in venom is spread over twice as large an area of the insect cuticle 
as the same concentration of control aqueous formic acid. He thus 
concludes that the white residue (amino acids) contributes to the 
toxicity of the formic acid by distributing the toxicant over a larger 
area than would be treated otherwise. However, it is worth bearing 
in mind that Stumper (1959) detected also an odorous constituent 
in the venom of a species of Formica. Stumper speculates that this 
volatile component may have arisen from the Dufour’s gland secre- 
tion, thus introducing the possibility that the secreted venom of 
formicines may contain products originating in two glands. In view 
of this distinct possibility, it is premature to attempt to explain the 
roles of poison gland products without considering the probably 
significant contribution to the toxicity of formicine venoms that the 
Dufour’s gland products may make. 
It should by no means be concluded that the chemistry of the 
formicine poison gland secretion is elucidated completely. The poison 
gland contents of C. penns ylvanicus contain, in addition to the de- 
scribed compounds, three compounds that reduce aromatic amino 
salts after the poison gland secretion has been subjected to thin layer 
chromatographic analysis. These compounds do not correspond to 
any amino acids, and they must represent unidentified constituents 
characteristic of the venom of this species. It may be no exaggeration 
to state that the elaborate formicine poison gland may yet be demon- 
strated to be a rich source of unsuspected natural products. 
SUMMARY 
Although Camponotus penns ylvanicus has well defined defensive 
mechanisims of biting and introducing acid into the wound, or merely 
the spraying of acid and other substances, some of the sclerites that 
take part in stinging in more primitive formicids are markedly re- 
duced in this species. However, the glands and reservoir regions 
associated with the apparatus are well developed. 
The white residue in the dry poison gland secretion consists of a 
series of 13 amino acids. Leucine, valine and serine are the major 
free amino acids present. The chemistry of formicine venoms and 
the possible roles played by their constituents are discussed. 
