ISSN:
1432-0762
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary 1. The defensive behavior of the termite Nasutitermes exitiosus (Termitidae, Nasutitermitinae) was studied in the field and laboratory. The termites were confronted with live arthropod enemies, mostly ants, and with animated mechanical dummies that served as surrogate enemies. 2. Both soldier and worker termites take part in the defensive actions. The weapon of the soldier is the secretory spray from its frontal gland, ejected from the pointed nozzle, or rostrum, at the front of the head. The spray is a viscous entangling agent, capable of quickly hindering the mobility of ants. The secretion also acts as an irritant, inducing scratching and other preening reflexes that in turn cause the sticky contaminant to be further spread over the surface of the enemy. Bioassays with cockroaches and flies showed irritancy to be attributable to such monoterpenoid components of the secretion as α-pinene and β-pinene. Scanning electronmicrographs of sprayed ants revealed that the secretion can also cause such incidental topical effects as spiracular occlusion and blockage of sensilla. The worker termites have no special weapons, but they can effectively bite. Ants may be crushed by the bites, or they may be slowed down by workers clamped to them with their mandibles and thereby rendered more vulnerable to being sprayed by soldiers. None of the ants, spiders, and centipedes presented to our termites in laboratory tests survived the encounters. 3. The soldier's secretion is an effective alarm pheromone. Once a target has been sprayed, other soldiers converge upon the site and deploy themselves around it. Attraction is effective up to a radius of 30 mm. Recruited soldiers add their own spray to target only if they are themselves assaulted upon arrival. Only direct contact stimulation causes soldiers to spray. The substance(s) in the secretion responsible for the alarm response remain(s) unknown. The workers are essentially unalarmed by fresh secretion. 4. Recruited soldiers tend to remain longer beside a “lively” sprayed enemy than beside one that has already ceased moving. As was apparent from the tests with mechanical dummies, the soldiers seem to gauge liveliness directly by contact, and by monitoring the slight air motions engendered in the immediate vicinity of the enemy by its movements. Conventional sound and substrate vibration appear to be of minimal importance in the detection of liveliness. 5. The attractiveness of discharged secretion to soldiers subsides with time, but more gradually than might be expected from an alarm pheromone. Even two days after discharge, secretion still elicits significant soldier approach rates. It is suggested that in nature, sprayed incapacitated enemies might be covered over by the workers with feces and soil, a behavior that could bring about a more timely blockage of the alarm signal.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00299954
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