Sexual deception, for males or herbivores?

Sexual mimicry when employed by orchids is incredibly effective, and in many orchids the deception is twofold. Counterfeit insect sex pheromones are released to attract male pollinators over long distances, and when within close proximity, the males are tricked once again with a floral structure visually resembling a female insect (Gaskett and Herberstein, 2010). This tactic is well documented in the Australian orchid species Cryptostylis, which targets a particular male wasp; Lissopimpla excelsa. Although sympatric Cryptostylis species share the same pollinator they never hybridize, even after hand cross-pollination, and their exact phylogenetic relationships are still largely unknown (Gaskett, 2012). 

Gaskett (2012) hypothesise that male pollinators display such strong affinity toward sexually deceptive orchids because normal mating behavior involves the engagement of several sensors, most of which the orchids successfully mimic and cater for. To attract male Lissopimpla excelsa wasps the Australian Cryptostylis send out a single odor compound, a compound which is shared throughout the species. Once attracted and within close proximity, the male wasps are then enticed to land on the flowers by red-orange wavelengths, yellow pollinia and UV reflections; which closely mimic that of a female wasps wings. This deception illustrates an incredibly species-specific mimicry of female wasps, while also exploiting the insect’s intrinsic attraction to UV and yellow wavelengths (Gaskett and Herberstein, 2010). Raised stripes and bumps on the flower surface indicate close mimicry of female wasp body length and thorax dimensions, which may be used to aid in a male wasps grip and help to align him in contact with the pollinia and stigma (Gaskett, 2012).

a C. erecta, b C. subulata,
c and d C. leptochila,
e C. ovata,and f afemale
L. excelsa wasp. Adapted from Gaskett and Herberstein (2010)

While many articles focus on the hypotheses that female wasp mimicry is employed to attract males and aid in pollination, another near forgotten hypothesis is being re-explored. This is the hypothesis that sexual mimicry is actually a sophisticated form of anti-herbivory defense. Lev-Yadun and Ne’eman (2012) revisited the notion that visual bee and wasp mimicry is not just for male pollinators, but also for herbivores. Because many herbivores associate bees and wasps with aggression and nasty stings they are avoided, hence the perceptual biases of herbivores toward these insects may cause a tentative approach to the sexually deceptive orchids and decrease their rate of herbivory (Lev-Yadun and Ne’eman, 2012).