Check our chapter in the book 'Chemical Ecology of Insect Parasitoids', by Eric Wajnberg and Stefano Colazza,
© 2013 John Wiley & Sons, Ltd. for more exciting phoretic relationships!

A hitch-hiker ’ s guide to parasitism: the chemical ecology of phoretic insect parasitoids
Martinus E. Huigens and Nina E. Fatouros

Abstract:
Phoretic arthropods use other animals as vehicles to migrate to new environments.
Among insect parasitoids, phoresy is almost exclusively restricted to
minute wasp species that develop in or on the smallest and most inconspicuous
life stage of their host: the egg. Females of about 35 egg parasitoid species are
known to hitch-hike with adult hosts to reach their egg-laying sites. Recent
studies suggest that phoretic parasitoids strongly rely on chemical espionage
to locate their transporting host. These wasps have evolved intriguing ways to
exploit cues that are part of their host ’ s communication system, including sex,
anti-sex and aggregation pheromones. Such a ‘chemical-espionage-and-ride’
strategy can be innate but it can also be learned. The extent and mechanisms
by which hosts might avoid exploitation are poorly understood. Here we discuss
why we expect phoresy to be much more widespread among egg parasitoids
than is known so far. It is expected to be adaptive, especially in those species
that have limited ability for directed fl ight, have a short time window available
for parasitism, have a narrow host range, and parasitize abundant hosts that
lay large eggs (or eggs in groups) with a large distance between them. We
review some recently published examples of chemical espionage by phoretic
egg parasitoids and discuss to what extent phoretic wasps represent a selective
force against the use of chemical cues by their hosts. At the end of the chapter
we identify unexplored aspects of the chemical ecology of phoretic insect parasitoids
that warrant further investigation. In addition to the fundamental interest,
research into the ways that phoretic parasitoids have evolved to locate their
host may help improve the effi cacy of using parasitoids as biological control
agents against insect pests.