Snippets from the linked articles are being used in the following summary under the Fair Use Clause of the U.S. Copyright Act, Title 17, Section 107.

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A species of termite found in the rainforests of French Guiana takes altruism seriously: aged workers grow sacks of toxic blue liquid that they explode onto their enemies in an act of suicidal self-sacrifice to help their colonies. The 'explosive backpacks' of Neocapritermes taracua grow throughout the lifetimes of the worker termites, filling with blue crystals secreted by a pair of glands on the insects' abdomens. Older workers carry the largest and most toxic backpacks. Those individuals also, not coincidentally, are the least able to forage and tend for the colony: their mandibles become dull and worn as the termites age, because they cannot be sharpened by moulting.
http://idle.slashdot.org/story/12/07/26/232211/exploding-termite-species-discovered


Jan Sobotnik from the Academy of Sciences of the Czech Republic and Thomas Bourguignon from the Université Libre de Bruxelles ... were studying the termite Neocapritermes taracua when they noticed that some workers have a pair of dark blue spots in the gap between their torsos and abdomens. When other termites attack their colony, the blue workers bite the intruders and burst, releasing a drop of fluid that soon becomes sticky gel. (Watch it happen in the video below – the black dot in the middle of the droplet are intestines and other internal organs).
http://blogs.discovermagazine.com/notrocketscience/


Old workers of Neocapritermes taracua develop blue spots on their abdomens that are filled with copper containing proteins. These react with a secretion from the labial gland upon autothysis to form a mixture which is toxic to other termites.
http://en.wikipedia.org/wiki/Autothysis