When you think of the word “pollinator” what comes to mind? For most people it will be bees, particularly the western honeybee (Apis mellifera). Some might also think of hoverflies, butterflies, moths, bats, hummingbirds…..but cockroaches?! The first published example that I know of which demonstrated that the flowers of a plant are specialised for cockroach pollination is from the mid-1990s. Since then only a handful of well documented cases have come to light, but there are undoubtedly more out there waiting to be discovered, particularly in the wet tropics. Most of the c. 4,600 species of cockroaches are nocturnal, and cockroach-pollinated flowers tend to open at night, which is one reason why they are under documented.
In a new study, published this week in the American Journal of Botany, a team of Chinese, German and British biologists has shown that a species of Apocynaceae from China is the first known example of cockroach pollination in that large family. Here’s the reference with a link to the study; if anyone wants a copy please email me:
The abstract for the paper follows:
Premise
Species of Apocynaceae are pollinated by a diverse assemblage of animals. Here we report the first record of specialized cockroach pollination in the family, involving an endangered climbing vine species, Vincetoxicum hainanense in China. Experiments were designed to provide direct proof of cockroach pollination and compare the effectiveness of other flower visitors.
Methods
We investigated the reproductive biology, pollination ecology, pollinaria removal, pollinia insertion, and fruit set following single visits by the most common insects. In addition, we reviewed reports of cockroaches as pollinators of other plants and analyzed the known pollination systems in Vincetoxicum in a phylogenetic context.
Results
The small, pale green flowers of V. hainanense opened during the night. The flowers were not autogamous, but were self‐compatible. Flower visitors included beetles, flies, ants and bush crickets, but the most effective pollinator was the cockroach Blattella bisignata, the only visitor that carried pollen between plants. Less frequent and effective pollinators are ants and Carabidae. Plants in this genus are predominantly pollinated by flies, moths and wasps.
Conclusions
Globally, only 11 plant species are known to be cockroach‐pollinated. Because their range of floral features encompass similarities and differences, defining a “cockroach pollination syndrome” is difficult. One commonality is that flowers are often visited by insects other than cockroaches, such as beetles, that vary in their significance as pollinators. Cockroach pollination is undoubtedly more widespread than previously thought and requires further attention.
It’s 3am here in Shenzhen. I fell asleep at 1030pm, worn out by the heat and activity of the day, but am now wide awake. In my head the tune to Millie Small’s 60s hit “
Prof. Jeff Ollerton - ecological scientist and author 