One last post on wasps, while I’m still on the topic.
Bees and spheciform wasps, forming the superfamily Apoidea, are hugely diverse in form, size, color, and habits. The rich variety within Apoidea can make the group difficult to recognize, but most share one particular morphological trait that, with practice, can reliably be used to diagnose these insects from other types of wasps.
The pronotum is the first big dorsal plate on an insect’s thorax, and in apoids this plate ends at the sides in a distinctly rounded lobe that does not touch the tegula, a small plate associated with the wing base. Bees, crabronids, sphecids, ampulicids, and other spheciforms have this distinctive pronotal lobe; similarly sized and colored wasps in the Vespoidea do not.
In contrast, here isEuodynerus, a vespoid wasp showing the non-apoid pronotum without the distinctive lobe:
In the previous post, I mentioned that Johnson et al (2013 ) determined the closest living relatives of ants to be “spheciform wasps + bees”. I assume we all know what a bee is, more or less, but what is a “spheciform wasp”?
Chances are, you’ve seen them. Spheciforms are everywhere, and their numbers include some of our largest and most colorful insects.
Spheciforms are a diverse assemblage of predatory & parasitic wasps abundant worldwide. Females construct nests to enclose offspring with prey, while the specifics of nest type and prey vary among species. Some fill mud nests with spiders, others stockpile bees in burrows dug into the sand, others stack aphids in nests tunneled through decaying wood. Size can vary from a few millimeters long to well over an inch; one of North America’s largest native wasps, the much-misunderstood Cicada Killer, is a spheciform.
One particular lineage of spheciform does exactly the same thing- constructing nests and provisioning them with food- only with pollen from plants rather than paralyzed insect prey. This group is the bees. Bees are built much like the rest of the spheciforms, but they have acquired a few specialized traits, like branched body hairs, that aid their pollen-feeding lifestyle and give taxonomists a way to identify them. Thus, bees are just vegetarian spheciforms.
I should also note, as a matter of clarification, what aren’t spheciform wasps. Many animals we often conjure when we think of wasps belong to other, non-spheciform groups. Paper wasps, yellow jackets, and hornets are vespid wasps, tarantula hawks are spider wasps, while the ubiquitous parasitoids belong to many older groups. Velvet ants are also not spheciforms, nor are they especially close relatives of ants.
Johnson et al’s discovery that spheciforms and ants are related is significant primarily from the observation that ants, too, build nests to raise their young. That all the insects in this group make enclosed nests, likely as an ancestral condition, and that this group contains several independent derivations of fully social, fully colonial behavior, should elevate the hypothesis that nest-building is a prerequisite for the evolution of sociality.
Current Biology has just published what is surely among the most significant papers this year on insect evolutionary relationships:
The importance of the paper derives from a combination of hitting a controversial topic with a much-needed phylogeny, and doing so with a staggering amount of information. The 300 or so genes employed to create the genomic tree is orders of magnitude more data than that used in any previous effort, and the result finally brings clarity to a question that’s been nagging a lot of Hymenopterists: what are the closest relatives of ants?
Probably, bees and spheciform wasps.
That’s not necessarily the relationship I would have guessed, but it holds under multiple modes of analysis.
Here’s the abstract (emphasis mine):
Eusocial behavior has arisen in few animal groups, most notably in the aculeate Hymenoptera, a clade comprising ants, bees, and stinging wasps. Phylogeny is crucial to understanding the evolution of the salient features of these insects, including eusociality. Yet the phylogenetic relationships among the major lineages of aculeate Hymenoptera remain contentious. We address this problem here by generating and analyzing genomic data for a representative series of taxa. We obtain a single well-resolved and strongly supported tree, robust to multiple methods of phylogenetic inference. Apoidea (spheciform wasps and bees) and ants are sister groups, a novel finding that contradicts earlier views that ants are closer to ectoparasitoid wasps. Vespid wasps (paper wasps, yellow jackets, and relatives) are sister to all other aculeates except chrysidoids. Thus, all eusocial species of Hymenoptera are contained within two major groups, characterized by transport of larval provisions and nest construction, likely prerequisites for the evolution of eusociality. These two lineages are interpolated among three other clades of wasps whose species are predominantly ectoparasitoids on concealed hosts, the inferred ancestral condition for aculeates. This phylogeny provides a new framework for exploring the evolution of nesting, feeding, and social behavior within the stinging Hymenoptera.
Source: Brian R. Johnson, Marek L. Borowiec, Joanna C. Chiu, Ernest K. Lee, Joel Atallah, Philip S. Ward (2013) Phylogenomics Resolves Evolutionary Relationships among Ants, Bees, and Wasps. Current Biology, Available online 3 October 2013. http://dx.doi.org/10.1016/j.cub.2013.08.050
No, not a bee eating a bee. Even better! This is a bee-mimicking robber fly, Laphria, feeding on a honey bee. The fly casually alighted next to me in the garden this afternoon, as though it wanted to be photographed with a trophy kill.
Laphria is an exemplary bumble bee mimic. The flies not only look like bumble bees, they move and sound like them as well.
photo details: Canon EF 100mm f/2.8 macro lens on a Canon EOS 7D ISO 400/800, f/14, 1/125 sec diffuse off-camera strobe, handheld overhead
As you may know, I teach photography workshops. We’ve got an outstanding one planned for September: BugShot Belize, and since we have a handful of registrations left I thought’d I’d mention a few prime reasons to attend.
And by “reasons”, of course, I mean the wonderful biota you’ll spend the week admiring.
Yesterday’s challenge required a fair amount of knowledge about the peculiarities of wasp development and morphology. Thus, I’m pleased the answers surfaced so quickly!
Here is a color photograph of the same species, a braconid wasp from Costa Rica:
Counting abdominal segments was tricky for two reasons. For one, most Hymenoptera have the first true abdominal segment fused to the thorax, so that functionally and visibly it is not part of what appears to be an abdomen. If this seems an obscure concept, I recommend watching ant, bee, or wasp brood in metamorphosis from prepupa to pupa. In many species, we can actually see the first abdominal segment move up and glom on to the thorax. In any case, abdominal segment counts in wasps start with what appears to be the back of the thorax.
Secondly, this particular family of wasps, Braconidae, has the dorsal plates of abdominal segments 3 & 4 fused. Thus, to count to the labelled segment in the challenge, you have to both recognize the fusion of abd 1 with the thorax, and abd 3-4 with each other.
Points are awarded as follows: 5 to Mr. I Love the Ants for counting correctly, 2 to Katherine for picking the family (though, not full credit for lack of supporting characters), 1 to Matt P for noting the fusion of 3&4, and 3 to Matt Bertone for noting the characters supporting the familial identification.