04 Jul Looking at the bigger picture
The Brittlebush (Encelia farinosa) is a beautiful desert plant with radiant yellow flowers. It grows in almost a bush-like bunch so it’s a breath-taking assortment of yellow and green. I see them every time I go out Tortoise tracking. Although, right now, in the middle of summer, they’re all dead. But I can imagine how amazing it looked in the spring. During one of my hikes with our volunteer Tom, I learned a little bit more about how the Brittlebush fits into the greater ecosystem around it. How the plant I walk by every single day, serves a larger purpose.
The Brittlebush produces a sap-like substance called pitch from their stem. This pitch was used by the Spanish actually as an incense! There something else, however, that has been using the pitch to their favor. Meet the Yellow-bellied Bee Assassin. Listen, I did not make that name up. The Yellow-bellied Bee Assassin is an insect, with a yellow belly, that sits on leaves and ambushes its prey – bees- killing them with venom. Like other insects, the Bee Assassin ovideposits its eggs on plant material. Having their eggs hang out on a leaf or bark is really vulnerable! Interestingly, the female Bee Assassin has been observed with this sticky area of plant resin on her abdomen. It’s been noted that the female will apply this resin to her eggs, deterring predators. Of course, as a scientist, you need hard evidence before coming to such a conclusion. That must be exactly what researchers from UC Riverside thought when they decided to collect and conduct trails on the Bee Assassin to answer this question once and for all. I love science for this reason, especially ecological science. Something perplexes you out in the field – make an experiment to answer your question!
Researchers collected Bee Assassins from Anza Borrego State Park (not too far from Joshua Tree) and conducted trails to identify the resin on the female’s abdomen, and to confirm if that resin deterred predators (ants). First, they identified the resin to be pitch from Brittlebush! The coolest part is how they figured out the function of the resin. The researchers had a box of ants where they introduced 3 different types of prey at different times, so they had a total of three experiments. First, they introduced eggs of the Bee Assassin, some coated in resin and some coated with a control substance. Then they introduced two different prey insects, fruit flies and cockroaches, also some with the resin and others without. In the end they found that the ants overwhelmingly preferred the eggs and insects without any resin on them. In some cases, they completely ignored the prey coated in resin! So, at least for now, it is confirmed that the brittlebush pitch is not only good for incense but also protects insect eggs from ants. Brittlebush is not only aesthetically pleasing to us, but most likely integral to the bug community here in Joshua Tree. It’s amazing to pick something I see everyday and fit it into the bigger picture. I can’t wait to continue to learn!