Today is the annual Verrall Lecture and Supper, a time for entomologists in the UK to gather in the vicinity of the Natural History Museum, looking uncharacteristically well-turned-out, and enthuse about insects over good food and wine. Taxonomists frequently bring pinned specimens of weird and wonderful species for show-and-tell, so it seems appropriate that the post today is all about a weird and wonderful insect. Or rather, three related species of weird and wonderful insects.
As a child, after barbeques on long summer evenings, we’d sometimes be sitting there in the garden when wasp workers (Vespula vulgaris, mostly) would fly down and start gnawing leftover scraps of meat from abandoned chicken legs and flying off with them. Most Vespid wasps are pretty partial to both meat and sugary liquids (hence the success of cola bottle traps). Bees, on the other hand, have given up their carnivorous ways and turned to exclusively plant-based diets.
Or have they…?
I found out about vulture bees recently and I decided they were weird and wonderful enough to warrant a little post.
Vulture bees are not like most bees. They are, to put it delicately, “obligate necrophages”.
Most bees eat nectar and pollen.
Vulture bees eat dead meat.
They were only really appreciated in the early 1980s, but a few people seem to have found them fascinating enough to engage in studies of their behaviour. The majority of work on them that I can find, at least recently, seems to have been done by David Roubik at the Smithsonian (who first published on them) and colleagues.
There are three main species, all in the genus Trigona: T. hypogea, the aptly-named T.
necrophaga and T. crassipes.
Their behaviour is nicely described by Noll (1997) and Roubik (1982)1, and isn’t so very
different from how common vespid wasps approach food sources, really. Apparently they won’t go for utterly rotten, stinking meat – they like it at least reasonably fresh.
Trigona, of course, are eusocial stingless bees – so after one individual finds a carcass, they rapidly recruit more foragers to the food source and soon you end up with many. It only takes a matter of minutes or a couple of hours after the first visit – till you can have between 40 and 108 bees on the carcass, which if you’re talking about something the size of a rat or lizard is quite some density of bees. They’re flexible – they’ll take brood from wasps’ nests in the right circumstances as well2 (interestingly, as normally it’s wasps doing this to bees!).
A little like flies, they feed by regurgitating saliva with a sort of honey-like concoction of fruit juices on to the food source and then lapping it up. The strange meat-mead mixture, if you can call it that, is then stored in honeypots much as their herbivorous cousins store regular nectar, honey or other sugar solutions! The three species don’t do it exactly the same way – T. hypogea seems to add a lot more nectar/juice, whereas T. necrophaga stores pretty much just meat “solution”.
They’ve completely given up gathering pollen – the workers don’t even have pollen combs on their legs any more. They have, however, occasionally been seen visiting stinkhorn mushrooms3 – if you’ve ever encountered a stinkhorn while walking in the woods, you can probably appreciate why, as they do smell quite convincingly like a dead fleshy thing! Apparently they may actually consume the spores (which are suspended in a goopy icky brown semi-liquid goo), and may also have a role in spore dispersal for these fungi.
Camargo and Roubik4 have looked into their anatomy in a bit more detail – it seems like apart from having fairly good mandibles and the lack of pollen combs, they’re not terribly exceptional, but usefully are able to produce antibiotic compounds in their salivary secretions (as a result of an interesting microbial gut flora). Which, if you’re eating raw meat, is probably helpful. Slightly more worryingly, Camargo and Roubik also comment that these bees produce a “sweet, clear honey…of unknown origin”. I am not altogether sure how they deduced that this honey was sweet, but as much as I like honey, when offered it from a nest where the bees were known to store partially-digested bushmeat broth I’d personally have given it a miss…
1Noll, F. B. (1997). Foraging behavior on carcasses in the necrophagic bee Trigona hypogea (Hymenoptera: Apidae). Journal of Insect Behavior, 10(3), 463-467 and Roubik, D.W. (1982) Obligate necrophagy in a social bee. Science 217 (4564), 1059–60.
2Mateus, S., & Noll, F. B. (2004). Predatory behavior in a necrophagous bee Trigona hypogea (Hymenoptera; Apidae, Meliponini). Naturwissenschaften, 91(2), 94-96.
3Oliveira, M. L., & Morato, E. F. (2000). Stingless bees (Hymenoptera, Meliponini) feeding on stinkhorn spores (Fungi, Phallales): robbery or dispersal. Revista Brasileira de Zoologia, 17 (3), 881-884.
4Camargo, J. M., & Roubik, D. W. (1991). Systematics and bionomics of the apoid obligate necrophages: the Trigona hypogea group (Hymenoptera: Apidae; Meliponinae). Biological Journal of the Linnean Society, 44(1), 13-39.