Ants

The infamous Rasberry Crazy Ant is Nylanderia fulva

Nylanderia fulva

A new ant invader along the U.S. gulf coast has gone variously by the names Rasberry Crazy Ant, Hairy Crazy Ant, Brown Crazy Ant, Nylanderia sp. nr. pubens, Nylanderia sp. nr. fulva, and probably others I’ve not heard. It’s a confusing mess that makes writing about this ant difficult and retrieving accurate information about it even more so.

Thankfully, a study out today in PLoS ONE by Dietrich Gotzek and colleagues has at least pinned down the Latin. Their verdict, after considering both morphology (mostly, the naughty male bits) and multiple genetic loci, is that the ant’s valid name is Nylanderia fulva.

Here’s a tree:

The imported ants are genetically nested within Nylanderia fulva. Adapted from Figure 3 in Gotzek et al (2012)

While the sample was geographically limited, the resulting topology does hint this new pest might come from the same part of the world- subtropical South America- as the famously troublesome fire ants and Argentine ants. Following up on this will require more extensive sampling in the Neotropics.

Disclaimers: I had a very small part in the research, in that I contributed the Paraguayan specimens to this study. Plus, lead author Dietrich Gotzek, in addition to being a stupendous molecular biologist, is also my cat-sitter. Thus, to the extent that our cats were well fed and their litter cleaned during our recent excursion to Belize, I find this to be an important and compelling study.


source:
Gotzek D, Brady SG, Kallal RJ, LaPolla JS (2012) The Importance of Using Multiple Approaches for Identifying Emerging Invasive Species: The Case of the Rasberry Crazy Ant in the United States. PLoS ONE 7(9): e45314. doi:10.1371/journal.pone.0045314

Strumigenys lujae

Strumigenys lujae (Kibale Forest, Uganda)

One perk of anting in Uganda was the lovely little Strumigenys lujae. Ants of this genus are cryptic and difficult to find in most parts of the world, yet in our corner of Africa S. lujae were in every rotting log and thick in the leaf litter.

I’ve posted a few new photos to my Strumigenys gallery.

An ant that protects herself with… um… butt foam

I’ve left you hanging long enough. Here is what Thursday’s mystery ant, an Asian Pachycondyla, does when bothered. She sprays foam from her venom gland.

Pachycondyla defensive foam takes two forms: stringy and clumpy. This ant demonstrates both.

This big tropical ant is a new addition to Andy Suarez’s University of Illinois research bestiary. A colony was collected by the recent multi-institutional Cambodian expedition for studies of ant venom chemistry, among other projects. A 1981 paper by Maschwitz et al describes the unusual defensive behavior:

When disturbed, two species of Malayan Pachycondyla release foam threads more than 10 cm in length or foam piles. The source of the proteinaceous foam is the enlarged venom gland, which is probably frothed up by air from the spiracles of the spiracular plates. The Dufour’s gland normally producing hydrocarbons in stinging ants is atrophied. Therefore, absence of the Dufour’s gland could be essential to the foaming ability, since the lipophilic hydrocarbons inhibit froth production in protein solutions. The release of foam is a mechanically acting defense mechanism, which is very effective against small mass-attacking ants. Pachycondyla species are also able to sting effectively.

I can vouch for their ability to sting effectively, too*.

When I don't let go*, the ant broadcasts more foam.
The froth is ejected so rapidly it gives the impression of silly string.
Close-up of the anal opening in bubble-blowing action.
Not done yet.
The sheer quantity of foam produced in only a few seconds is astounding.

*no ants were harmed in the making of this post, and the colony was rewarded for their participation with several fat crickets. I, on the other hand, discovered that the ants have a more conventional defense, too: a good, old-fashioned stinger.


source: Maschwitz U, Jessen K, Maschwitz E (1981) Foaming in Pachycondyla: a new defense mechanism in ants. Behav Ecol. Sociobiol 9:79-81.

Velcro Hairs Allow Ants to Hang Their Larvae

If you’re like me (and I know many of you are), you spend a fair amount of time poking about in ant nests. Nests usually contain developing larvae, of course, which some species maintain in an ungainly pile. In others, young are spaced along the walls and roof of the chambers. Like so:

Pheidole floridana larvae adhered to the roof of their brood chamber. Note how the larvae are all oriented with their backs to the substrate. These were stuck to the underside of a rock that I flipped, exposing the nest. (Austin, Texas).

How do ants hang their larvae? Thanks to a simple experiment published today by Clint Penick in PLOS ONE, now we know: larvae of a particular age have little anchors.

Schematic (A) and scanning electron micrograph (B) showing the anchor-shaped hairs on a larva of the harvester ant Pheidole rhea. Modified from Figure 1 of Penick et al 2012.

Not all larvae of all species have these hooked hairs. Rather, the structures appear in older instars of several disparate myrmicine genera like Pheidole, Cephalotes, Crematogaster, Strumigenys and Temnothorax, among others. I had a look through my old photos. Sure enough, for the indicated taxa, many larvae appeared hairy and/or stuck to something.

sgs
The larva at left in this image of a Crematogaster emeryana brood nest shows the anchor hairs.

To confirm the  function of the anchor hairs, Penick et al performed an obvious test of the velcro hypothesis: They gave the grubs a haircut.

If the larvae still adhered to the test walls, some other mechanism must be at work. If the larvae fell, the hypothesis is supported. How well did shorn larvae stick?

Larvae with their anchor hairs cut dropped like rocks compared to anchored controls. Modified from Figure 3 of Penick et al 2012.

Poorly, if the walls were vertical, and hardly at all at greater angles. An elegant result! It appears the hairs-as-anchors hypothesis is correct.

And as far as I know, this may be the first time ant babies have been given haircuts for science.


source: Penick CA, Copple RN, Mendez RA, Smith AA (2012) The Role of Anchor-Tipped Larval Hairs in the Organization of Ant Colonies. PLoS ONE 7(7): e41595. doi:10.1371/journal.pone.0041595

A simple twig ant, Pseudomyrmex simplex

Pseudomyrmex simplex (Minas Gerais, Brazil)

Among the more common twig ants across the Neotropics is the pleasingly orange Pseudomyrmex simplex. I somehow managed to avoid photographing it until our recent Brazilian adventure, however. Here are a couple shots of workers carrying larvae to safety after I split open a small twig containing a satellite nest.

As these ants are shiny, photographs of them are prone to glare if the light is not sufficiently soft. Here, I spent extra time arranging my mylar diffuser to get the lighting right.

Pseudomyrmex simplex (Minas Gerais, Brazil)

photo details: Canon MP-E 65mm 1-5x macro lens on a Canon EOS 7D
ISO 200, f/13, 1/200 sec
diffuse twin flash

Camponotus impressus, a cork-headed ant

One of Josh King’s lab ants at the University of Central Florida. The blunt head serves as a living door to this species’ twig nests.


photo details:
Canon MP-E 65mm 1-5x macro lens on a Canon EOS 7D
ISO 200 f/13 1/250 sec
diffuse twin flash

Benoit Guenard figures out the easiest places to record new ant genera

If you follow myrmecology on the internet, you probably know about Benoit Guenard’s Global Ants database. Benoit has spent years combing disparate biological literature and natural history collections to compile a comprehensive map of where all the 300-some ant genera are known to live. This information is useful in its own right (want to know which ants live in that tropical vacation destination?) but the database is more powerful that that. It can be used to make predictions about where in the world we are most and least likely to make new genus & species records.

Top: the number of ant genera recorded from various political divisions (darker=more). Bottom: model predictions of undercollected regions (yellow & blue are different models; black is where both models agree). Modified from Figures 1 & 3 in Guenard et al 2012.

In a clever paper out this week in the Proceedings of the National Academy of Sciences, Benoit and his colleagues Michael Weiser and Rob Dunn apply a pair of mathematical models to the database to locate spots on the map with far fewer known ant genera than their location might predict. Because ant researchers have tended to work more in particular countries and less in others, what this project has effectively done is pinpoint the under-studied corners of the globe. Places where even common ants have gone uncollected.

Off to Cambodia it is, then.


source: Guenard, B. et al 2012. Global models of ant diversity suggest regions where new discoveries are most likely are under disproportionate deforestation threat. PNAS published online before print doi:10.1073/pnas.1113867109.

The eastern ant cricket Myrmecophilus pergandei

Myrmecophilus pergandei

If you look closely when opening large ant nests in the northern hemisphere temperate zone, there is a good chance you’ll see ant crickets. These flattened, wingless insects are kleptoparasites living among ant colonies, stealing food and tricking the ants into feeding them.

Ant cricket in a nest of odorous house ants

The common species where we live in the midwest is the eastern ant cricket Myrmecophilus pergandei. Larger nests of Tapinoma sessile in our yard often have a few of these running about, so this morning I borrowed one for a twenty minute studio session. They’re odd looking animals, but then, they have an odd lifestyle.

For the rest of the photos, click here.


sources:
MacGown, J.A, Hill, J.G. 2006. The Eastern Ant Cricket, Myrmecophilus Pergandei Bruner (Orthoptera: Myrmecophilidae), Reported From Mississippi, U. S. A. Journal of the Mississippi Academy of Sciences 51: 180-182.

photo details:
Canon MP-E 65mm 1-5x macro lens on a Canon 7D
ISO 200, f/13, 1/250 sec
diffuse flash

Tetramorium bicarinatum

All this talk about copyright infringement is a real downer. It’s time to perk things up with pretty ants:

Tetramorium bicarinatum workers gather nectar from glands of an invasive mallow. Some plants use nectar to attract ants as a defense against herbivorous insects, as ants also eat insect eggs and caterpillars. (Orlando, Florida, USA)
A more field-guidey shot of T. bicarinatum. This ant is presumably native to Asia, but thanks to global trade is now found in warmer climates worldwide.