Evolution

There is a constant evolutionary race between host and parasite, particularly in the case of social insects. As parasites evolve to better escape detection, social insects evolve to better detect them.

One example of this is the myrmecophilous (ant-loving) silverfish Malayatelura ponerophila, which makes its home in the nest of the army ant. As army ants have limited eyesight, chemical cues (sce

nt in particular) are the main way they recognise fellow colony members. They will kill any insects they do not recognise as their own - they have been known to kill other army ants if they smell like they're from a different colony. It's certainly a dangerous way for silverfish to live.

So how do they escape detection? They rub themselves against immature ants and "steal" their scent. This coats the silverfish in chemicals known as cuticular hydrocarbons (CHCs). A study on the army ant-silverfish relationship discovered that while ants have around 70 CHCs, silverfish have zero. Researchers tagged the immature ants with a radioactive HC and found silverfish acquired this marker soon after. Army ants acted more aggressively to silverfish who had been isolated (and so lost their stolen CHCs).

This chemical mimicry is just one way myrmecophilious organisms can survive in ant nests. Other parasites have been found to synthesize chemicals or adopt behaviours to avoid detection. This arrangement certainly works out well for parasites, who have free food and shelter without giving anything in return - unless they're caught, in which case the cost may be their life.

Photo: A myrmecophilous silverfish (credit to Josh D. Kouri).

http://www.sciencedaily.com/releases/2011/11/111130202559.htm

http://blogs.discovermagazine.com/discoblog/2011/12/05/impostor-silverfish-rub-up-on-adolescent-ants-to-create-their-smelly-disguises/

A paper on the silverfish-ant CHC experiment is available here:
http://www.biomedcentral.com/1472-6785/11/30