Olfactory detection of prey by the termite-raiding antPachycondyla analis

Abstract

The African termiteraiding ant Pachycondyla analis Latreille (Hymenoptera: Formicidae) organizes group raids on termites of the subfamily Macrotermitinae. Termites and ants occupy and share similar habitats, resulting in a co-evolutionary arms race between termites as prey and ants as predators. The present study explored whether P. analis uses semio- chemical signaling cues to detect potential termite prey prior to and during raids. Ants' responses to odors emitted from termites alone, termite gallery soil, and termites inside their galleries were tested using Y-tube olfactometer assays. The results showed that P. analis detected odors of termites and those of their galleries, and odors from termites inside their galleries were more attractive to both minor and major ant workers than odors from termites alone. The composition of these odor sources was identified using gas chromatography-mass spectrometry analysis. While the odors from termite gallery soils were compositionally richer (containing 13 compounds rather than nine from termites alone), those from the termites alone were quantitatively richer, releasing about six times more odors than gallery soil. Most of the compounds in the odor profiles were identified as hydrocarbons. Naphthalene, previously identified as an insect repellent, was also identified as a component of the odors from the gallery soil. These results demonstrate that odors play an important role in prey detection by P. analis.

Keywords: Matabele ants; Megaponera foetens; Ponerine ant; odors; olfactory cues; termite gallery soil.

Figure 1.

Preferences of Pachycondyla analis major and minor workers for odors from: A. Odontotermes sp . gallery soil; B. Odontotermes sp. workers and soldiers; and C. Odontotermes sp. and gallery soil when presented alongside clean air. Black bars represent response to odors, white bars represent response to the control. Numbers within bars refer to the number of ants making a choice, and numbers outside bars refer to ants that made no choice (N = 30 each for major and minor workers in each test, ** = significant at P < 0.05 and *** = significant at P < 0.001). High quality figures are available online.

Figure 2.

Preferences of Pachycondyla analis major and minor workers to odors from Odontotermes sp. (workers and soldiers vs. odors from Odontotermes sp. in gallery soil. Black bars represent response to odors from termites in gallery soil, white bars represent response to odors from termites only. Numbers within bars refer to the number of ants making a choice, and numbers outside bars refer to ants that made no choice. N = 30 each for major and minor workers in each treatment, ns = not statistically significant at α = 0.05. High quality figures are available online.

Figure 3.

GC-MS trace of chemical compounds extracted from: A. ~2 g of Odontotermes sp. gallery soil, and B. 10 Odontotermes sp. workers. Labeled peaks are: 1) n - heptane; 2) n - octane; 3) α-Phallendrene; 4) naphthalene; 5) Butanoic acid-tridecyl-ester; 6) 2-Napthalenemethanol; 7) Methyl-carbinol; 8) n - heptadecane; 9) n - eicosane; 10) n - tetracosane; 11) n - pentacosane; 12) hexylpentadecane; 13) 13-undecylpentacosane; 14) n - octacosane; 15) 1-Nonadecene; 16) Oxalic acid, hexyl pentadecyl ester; 17) squalene. High quality figures are available online.