Formosan subterranean termite (Isoptera: Rhinotermitidae) frontal gland secretion and their fatty acid constituent activity on termites and red imported fire ants (Hymenoptera: Formicidae)
Although the frontal gland secretion of Formosan subterranean termite (Coptotermes formosanus Shiraki) makes up to 36% of the soldier body weight and is secreted when engaging in defensive and aggressive interactions, very little is known about what and how it functions. We evaluated the frontal gland secretion of this species and seven recently identified saturated fatty acid constituents for their effect on soldier caste formation in Petri dish bioassays. The behavioral and toxic effects of the fatty acid constituents also were evaluated against both C. formosanus and the red imported fire ant (Solenopsis invicta Buren), a natural predator. The frontal gland secretion was found to have no effect on termite soldier formation, but its fatty acid constituents stimulated soldier production. Termite workers in fatty acid treatments took less time to form pre-soldiers and soldiers than did controls. At 40 days post treatment (the end of experiment) more soldiers were produced in myristic (C14:0), palmitic (C16:0), stearic (C18:0), and hexacosanoic (C26:0) acid treatments when compared with the control. Stearic and behenic (C22:0) acid treatments showed some short term repellency to termites and stearic and arachidic (C20:0) acids reduced termite tunneling activity. Palmitic acid increased termite tunneling. No fatty acids tested were toxic to termites. There was no observable behavioral or toxic effect on red imported fire ants.