Supplementary materials for: Striking cuticular hydrocarbon dimorphism in the mason wasp Odynerus spinipes and its possible evolutionary cause (Hymenoptera: Chrysididae, Vespidae)

Cleptoparasitic wasps and bees smuggle their eggs into the nest of a host
organism. Here the larvae of the cleptoparasite feed upon the food
provision intended for the offspring of the host. As cleptoparasitism
incurs a loss of fitness for the host organism (offspring of the host fail
to develop), hosts of cleptoparasites are expected to exploit cues that
alert them to potential cleptoparasite infestation. Cuticular hydrocarbons
(CHCs) could serve as such cues, as insects inevitably leave traces of
them behind when entering a nest. By mimicking the host's CHC
profile, cleptoparasites can conceal their presence and evade detection by
their host. Previous studies have provided evidence of cleptoparasites
mimicking their host's CHC profile. However, the impact of this
strategy on the evolution of the host's CHC profile has remained
unexplored. Here, we present results from our investigation of a
host-cleptoparasite system consisting of a single mason wasp species that
serves syntopically as the host to three cuckoo wasp species. We found
that the spiny mason wasp (Odynerus spinipes) is able to express two
substantially different CHC profiles, each of which is seemingly mimicked
by a cleptoparasitic cuckoo wasp (i.e. Chrysis mediata and Pseudospinolia
neglecta). The CHC profile of the third cuckoo wasp (Chrysis viridula), a
species not expected to benefit from mimicking its host's CHC profile
because of its particular oviposition strategy, differs from the two CHC
profiles of its host. Our results corroborate the idea that the similarity
of the CHC profiles between cleptoparasitic cuckoo wasps and their hosts
is the result of chemical mimicry. They further suggest that
cleptoparasites may represent a hitherto unappreciated force that drives
the evolution of their hosts' CHCs.