Fontanellar gun

The fontanellar gun is a type of specialized weaponry used by the soldiers of the North American termite subfamily Nasutitermitinae to ward off predators. Located on the front of the soldier termite's face, the "gun" is a chemical reaction that is triggered when the termite contracts its mandibular muscles, which is "able to eject the frontal gland material over a distance of many centimeters".^[1] The gland material is forced out through the front of the internal nose and its pores, which covers much of the termite's head. The North American Termite has been shown to be extremely accurate with the gun, even though it, like most termites, is blind. The exact nature of how the termite is so accurate and is able to orient itself toward its enemy is currently unknown, but it is believed that the ability is "olfactory or auditory" in nature.^[1] In some North American termite subspecies, when the glandular secretion is fired, it rips off the termite's mandibles, forcing it to retreat back into the nest.^[2] However, the North American Termite has evolved as such that its mandibles in and of themselves offer little protection or defense, so the loss of them does not hinder the termites. It is also possible for the termites to fire their gun more than once, if the threat that caused them initially to fire continues to exist.^[3]

The fired material is glue-like and sticks to objects that it hits, causing the legs of an attacking enemy to become stuck to the ground. Most often, though, a number of termite soldier ants will fire upon the enemy and the combined force of the "bullets" will kill the enemy along with covering it in the glue-like substance. It has also been observed that, for those that survive the force of the material, it also causes varying negative effects, likely because of the terpenes contained in the compound. Eventually, if not killed from other effects, the secretion of the termite will kill any enemy insects after 24–48 hours. In comparison, the effect of the secretion on termites of the same species was considerably worse, with the secretion causing death within 5–6 hours.^[3]

Chemical composition

Chemical composition tests discovered that the secretion contained 62% pinene, 27% myrcene and 11% limonene. Together, these three compounds create a type of terpenes, commonly known as pine resin. After comparison to similar secretions from termites outside of North America, whose compounds had been found to be non-toxic, it was determined that the glandular secretions of the North American termite were "definitely toxic" for insect species.^[3]

It is believed that the secretion contains an alarm pheromone that alerts other soldier termites of an enemy attack and causes them to fire their fontanellar gun. It was discovered that the pinene was also acting as an alarm pheromone while it was forming the composition of the terpenes. Because later arriving termites did not also fire their gun, it is believed that the pinene pheromone lasts for only a brief period of time before dissipating.^[3]

References

1. O. Wilson, Edward (2000). Sociobiology: the new synthesis. Harvard University Press. pp. 302–305. Retrieved July 22, 2011.
2. Kerkut, G. A. (1985). Comprehensive insect physiology, biochemistry and pharmacology: Embryogenesis and reproduction. Pergamon Press. p. 262. Retrieved July 22, 2011.
3. W. L. Nutting; M. S. Blum; H. M. Fales. (1974). "Behavior of the North American Termite, Tenuirostritermes tenuirostris, with Special Reference to the Soldier Frontal Gland Secretion, Its Chemical Composition, and Use in Defense". Psyche. Hindawi Publishing Corporation. 81 (1): 167–177. doi:10.1155/1974/13854. Retrieved July 22, 2011.