Plociopterus ain't no myrmecophile!

In a paper just published in Coleopterists Bulletin (pdf here), Mariana Chani-Posse and I moved two myrmecophilous species of “Xanthopygina” in Philonthina. Both species had been described by Wasmann 1925 in the genus Plociopterus. And so for the last 90 or so years, Plociopterus was known to have two myrmecophilous species. Unfortunately, several authors discussing the origin of myrmecophily in Staphylinidae (or at least specifically for Staphylinini) was using this as an example of independent evolution of myrmecophilous life style. The problem was that nobody had checked the specimens since the original description, because none of those species belonged in Plociopterus. They are Belonuchus (at least until the genus is revised) and for those keeping score at home, this is also the wrong subtribe…

The moral of the story is this: people make mistakes and generic concepts change over time, as well as our understanding or higher level relationships. As I have mentioned earlier, If somebody described a taxon 100 years ago, chances are that this taxon now belongs in a different genus or is a synonym of something else. Using raw data in biodiversity studies without going through the lens of a revision is almost guaranteed to lead to erroneous results.

As a side note, Plociopterus is in terrible need of a revision. There are multiple new species awaiting description and many taxa that have to be placed in synonymy. But the genus has an infamous history among Xanthopygina workers: at least twice people have started its revision (both in the lab of my late PhD advisor, Steve Ashe) and both times people abandoned the effort. Perhaps third time’s the charm?

Ten facts about rove beetles

I wrote a small blog post hosted by Christopher Buddle at Expiscor.  The post is about what I thought were 10 really cool things about rove beetles. Go read it here.

Working with a Darwin specimen

Today a paper came out where I describe a new genus and species of rove beetles. The description was based on just two specimens, one from the Natural History Museum, London and one from the Museum für Naturkunde der Humboldt Universität, Berlin. We typically want to have more specimens before we describe a new species. However, I decided to go ahead with the paper for two reason (1) I have been visiting major (accessible) entomological collections for more than 12 years and I have not seen other specimens and (2) one of the specimens was collected by Darwin himself!

Below is a photograph of the holotype of the new species, Darwinilus sedarisi Chatzimanolis.

Image Copyright, The Natural History Museum, London.

The Darwin specimen was collected in 1832 and there are traces of (non water-soluble) glue on the ventral side of the specimen. You undoubtedly noticed that the specimen is "dirty".  I did not attempt to "clean" it, either physically or post processing (i.e., in Photoshop). I was both in awe and scared to death handling the specimen, so I really tried to minimize time spent handling it. To dissect the genitalia I followed the steam method described by Beulah Garner (curator of Coleoptera in the Natural History Museum, London). But I did not attempt to relax the mouthparts of move the legs, a standard practice on more recent specimens, as I did not want to press my luck.  

Here is a close up of the head, where all the dust is visible in exquisite detail:

Image Copyright, The Natural History Museum, London.

I know I could have very easily cleaned the specimen with a fine paintbrush. But in a specimen as old as this, who am I to say that the dust does not belong there, especially when it does not affect the specimen description?  In a later post I will write about how I stumble upon the specimen. 

Dumpster diving xanthopygine rove beetles

Let's face it, a lot of beetles are associated with ants. But few go to the extremes that rove beetles go to make themselves at home with the ants. Many rove beetles not only look like ants, they also smell like ants. If you want to see some really cool, yet ultimately bizarre beetles, I suggest you read the blog post by Joe Parker and Taro Eldredge on Pselaphinae and Aleocharinae myrmecophiles.

A few xanthopygine rove beetles are known to be associated with ants but these beetles are typically found on ant refuse piles (=dumpsters). The refuse piles are nutrient-rich, thriving micro-communities that support many types of arthropods, fungi and bacteria. Most rove beetles are there to feed on the fly larvae but we really do not know the details. Navarrete-Heredia (2001)* lists 65 genera (148 species) of rove beetles associated with leaf cutter ants, either Atta or Acromyrmex. Several xanthopygine beetles made the list, including species from the genera Glenus, Paraxenopygus, Tricholinus, Scariphaeus, Smilax and Plociopterus.

Glenus jelskii Solsky is known from refuge piles of Atta sexdens (Scheerpeltz 1936)

One striking feature of all these xanthopygines is that they are good-looking beetles. I would have expected that an insect hiding in a refuge pile would be dull-colored (why spend energy on coloration?) but most of these have shining metallic colorations with bright yellows and reds. Not sure if this is a plesiomorphic characteristic (most xanthopygines have impressive metallic coloration) or if there is an adaptive significance of the coloration.

Some xanthopygines take their Hymenoptera associations one step further: they are known from debris piles of wasps and stingless bees. One of largest (almost 3 cm) known xanthopygine rove beetle, Triacrus dilatus, is known from the debris piles of the wasp Stenopolybia Agelaia vicina (Wasmann 1902).

Triacrus dilatus Nordmann

A couple more species, Xanthopygus cyanipennis and Xenopygus analis have been recorded from the nest of Trigona clavipes (a stingless bee) (Luderwalt 1917), although both of these instances might be accidental/opportunistic. Xenopygus analis is extremely widespread (Mexico to Brazil, introduced in Hawaii) and will feed on anything. A while back I posted a video clip of X. analis eating rotting Gustavia superba fruits.

A lot of cool work remaining to be done here, both systematic and ecological, to understand these associations and map the evolution of these behaviors.


*Thanks to Adam Brunke for providing some of these references.

References

Luderwalt H (1917) Biologishes uber brasilianische Staphyliniden. Z. Wiss. Insektenbiol. 13: 44-47

Navarrete-Heredia JL (2001) Beetles associated with Atta and Acromyrmex ants (Hymenoptera: Formicidae: Attini). Transactions of the American Entomological Society 127(3): 381-429.

Scheerpeltz O (1936) Die von Prof. Dr. H. Eidmann gelegentlich seiner im Jahre 1933 nach Brasilien unternommenen Studienreise aufgesammelten Staphyliniden. I. Die in den Nestern von Atta sexdens L. aufgefundenen Staphyliniden, nebst einigen Bemerkungen uber die Gattung Scariphaeus Er. Archiv fur Naturgeschichte (N.F.), 5, 483–540.

Wasmann E (1902) Riesige Kurzflügler als Hymenopteren-Gäste. (132 Beitrag zur Kenntniss der Myrmekiphilen und Termitophilen.). Insektenborse 19: 267–268, 275–276, 282.

The limits of morphology

I was told early on as a graduate student that an insect taxonomist should "kill first, ask questions later" during fieldwork. This was usually said in the context that you might lose a rare specimen if you spend time looking at it, rather than putting in a vial. I am here to tell you that I have deeply regretted following that advice.

Every single time I am working on a taxonomic paper I catch myself having the same wish: "I wish I had seen these specimens alive, just to get a glimpse of how they are using these structures." Morphology can tell us a lot of things but sometimes a dead insect hold its secrets very well.

Exhibit A: In a paper published in 2005, Steve Ashe and I revised the genus Philothalpus. These are striking beetles with questionable taxonomic affinities (at least according to DNA).

Philothalpus brooksi

Abdominal sternum VII

Males in this genus have a perplexing structure (indicted by a white arrow on the figure above) on the ventral side of their abdomen, specifically on the 7th abdominal sternum. Back then we called it a "porose structure". Truth is, we have no idea what it is. A hole on the body with setae around it. Only males have it. But how do they use it? I have no clue. I guess I will be inclined to accept the notion that is used in male/female interactions since it is only present in males but, boy, if only I had seen these guys alive...

The example above came to mind when I recently examined a species (in another genus) with a similar structure:

Exhibit B:

 The structure is present in the same abdominal segment (VII) but it is clearly different than the one above. Are these structures homologous?  Are they used for the same purpose? Morphology cannot answer these questions. Sure, we can do fancy evo-devo here, but that requires live specimens, identifying conserved developmental genes and so on.

What we really need is good old basic natural history observations that can solve these problems. But "kill first, ask questions later" attitudes really do not help. So, next time you are in the field, jot down some observations before you kill those insects.

Natural History with toddler

Lately after I pick up my daughter from daycare, we come home and we go sit on the bench in the backyard. I call this the "Banana/Natural history time" and typically involves her eating a banana, while we both unwind from our day activities. This is becoming fast my favorite time of the day. As mentioned in a famous book series "The world is quiet here" during that time.

The above-mentioned toddler during snack time

Right behind the bench, there is a little patch (maybe 1x2 square meters) of native plants. Inspired by David Haskell's book (The Forest Unseen) we have been doing daily natural history observations during the "banana time".

We have been watching ants digging new tunnels, blue-eyed grass flowering, azalea's dropping their flowers and creating pulp-like substrate and bryophytes producing their sporophytes. Now, I do realize that my 21 month daughter cannot assimilate most of that, but you got to start them early, right?