Identification of hydrocarbons that protect ticks (Acari: Ixodidae) against fire ants (Hymenoptera: Formicidae), but not lizards (Squamata: Polychrotidae), in an allomonal defense secretion

Abstract

To explore allomonal (= defensive) function, select hydrocarbons identified in a tick defense secretion (Dermacentor variabilis) were topically applied onto mealworm larvae and offered to fire ants and anoles. In particular, n-C₂₀, n-C₂₄ and methyl branched n-C₂₅ alkane treatments protected mealworm larvae against ants, and were as effective as squalene (C₃₀ alkene), the secretion's principle component, for preventing attack. Given that the tick allomone is not an obnoxious repellent, it is suspected that hydrocarbons probably blunt antennal chemosensory receptors, which block aggressive responses by the ants. This protective secretion ‘hides’ the tick, which along with mobility permits escape. There was no adverse reaction to natural tick secretion by anoles, allomone-depleted (secretion-exhausted) ticks were not eaten and topically applied natural secretion and its components failed to rescue treated mealworms from predation. Of interest is that the efficacy of the tick allomone compares favorably to the majority of defense secretions in insects, especially those that function uniquely against ants.

Key words :

• Allomone
• defense
• hydrocarbon
• tick
• ant
• lizard
• anole