"Sneaky" Fig Wasps in South Africa - Observation of the Week, 6/28/22

Our Observation of the Week is this pair of fig wasps (Watshamiella alata on the left, Sycoscapter cornutus on the right), seen in South Africa by @alandmanson!

In July of 2020, during COVID lockdown, Alan Manson began observing the wasps on the twenty-five year old fig tree in his backyard. As you may know, figs are only pollinated by certain wasps in the Family Agaonidae (they have amazing heads, by the way), but many other wasps both in that family and in others do not pollinate figs, they induce galls in fig plants, and both of the wasps you see above are of the latter variety. 

However, there's a reason the Watshamiella alata wasp is following the Sycoscapter cornutus wasp, which Alan discovered while learning more about fig wasps from FigWeb and @simonvannoort. Compton, et al, in their paper "Sneaky African wasps that oviposit through holes drilled by other species" (open access) found that female wasps in the genus Watshamiella will follow other female fig wasps and, after that female “drills” a hole in the fig and oviposits, the Watshamiella will oviposit into the same hole. 

So when I saw the female Watshamiella alata watching a female Sycoscapter cornutus oviposit, I realized that I might be able to catch the former using the same hole for its own eggs. Eight long minutes later the Sycoscapter departed and I was able to photograph the Watshamiella place her ovipositor into the same hole. 

The exact nature of the interaction between the larvae of these wasps is unknown, but Compton, et al believe the oviposition behavior has several adaptive advantages for the Watshamiella wasps:

• they don’t need the larger anatomical structures necessary for drilling into the fig.
• they don’t need to expend the large amount of energy needed for drilling into the fig.
• oviposition is much quicker for the Watshamiella wasps, reducing their vulnerability to predators such as ants, which often patrol figs. 

Alan (above, in the Mkomazi River) tells me he grew up on the a farm in the KwaZulu-Natal of South Africa, and birded, herped and fished when he was a child, which led to his career in soil science. He credits digital photography with getting him into bird photos, and the Southern African Bird Atlas Project 2 for getting him into citizen/community science, and he joined iNat in 2017. Since getting to wasps in 2019, Alan uses iNat mostly for wasps now, but says

I use iNaturalist to archive the biodiversity I am able to capture wherever I take out my camera. Digital photography has changed the way I see the natural world, as it forces me to ignore the bustle of the human world and focus my attention on the subject of the moment. iNaturalist allows me to archive those experiences and, along with many other online resources, to learn more about the organisms I have photographed.

(Photo of Alan by KD Dijkstra, it was cropped in order to better fit into our blog format.)

- Alan’s linked to other observations associated with this fig tree here.

- the fig-wasp pollination process is pretty remarkable, here’s a video depicting it.

- two other Observations of the Week document wasps ovipositing into plants: this one by @ropro, and another by @cholmesphoto.

Posted on June 28, 2022 09:00 PM by tiwane