Archive for Introduced Ants

Antkey Mobile released

The USDA APHIS ITP team is pleased to announce the latest addition to our mobile app collection: Antkey Mobile. Developed in cooperation with the tool’s author, Eli Sarnat, and Australia’s Identic team, this app is based on ITP’s web-based tool, Antkey.
Lucid Mobile apps offer you the identification keys you’ve come to rely on from the convenience of your smartphone or tablet. Antkey Mobile (free for Android or iOS) allows you to take your Lucid key with you into the field for surveys and screening, even if your field site lacks internet access.
This key allows both specialists and novices to easily identifyinvasive, introduced, and commonly intercepted ant species from across the globe. You can help confirm whether you have found the correct species by comparing your specimen with the images and descriptions on the fact sheets, which are included for each species.

Tramp ant caught globetrotting under false name


Tramp ant caught globetrotting under false name

December 14, 2015
Tramp ant caught globetrotting under false name
A specimen of Pheidole indica, an ant species from Asia that has been spreading across the globe under the name Pheidole teneriffana. Credit: Dr. Eli Sarnat

A century-old mystery surrounding the origin of an invasive ant species was recently solved by an international team of scientists. Since 1893, when it was first discovered as an invasive species in the Canary Islands, entomologists have been debating where this mystery species came from. While some insisted on the Mediterranean, some proposed Arabia and others argued for Africa. The correct answer? Asia.

The authors of the study, published in the open-access journal ZooKeys, solved the taxonomic puzzle by fitting together disparate pieces of evidence. “I was having a terrible time trying to distinguish this one Asian from the mysterious ant that was coming in on shipments from the Caribbean, Europe and Africa,” says Dr. Eli Sarnat, University of Illinois, about his research at the Smithsonian on tramp that were intercepted at US ports.

Tramp ants, many of which are pest species, are spread across the globe by stowing away in the cargo of ships and planes, thus posing rising environmental, food security and public health concerns.

The same day Sarnat was working on the mysterious ant in the Smithsonian, he received an email from Dr. Evan Economo, Okinawa Institute of Science and Technology (OIST). Economo and Dr. Georg Fischer, also affiliated with OIST, had included Madagascar samples of the species in a genetic analysis, and the results unexpectedly placed it within a group of Asian species. The closest genetic match to the enigmatic ant turned out to be the very same Asian species that Sarnat had found in the Smithsonian collection.

Tramp ant caught globetrotting under false name
A showing the global distribution of Pheidole indica, with the native regions in blue and the invaded regions in red. Credit: Dr. Eli Sarnat

The last piece of the riddle was discovered thanks to the painstaking work of Dr. Benoit Guénard. Guénard, a professor at the University of Hong Kong, had spent years mapping the global distributions of every ant species known to science. When he compared the ranges of the mysterious ant with the common Asian species, the two fit together like a jigsaw puzzle.

Evidence gathered from classic taxonomy, modern genetic analysis, and exhaustively researched distribution maps all pointed to the same conclusion.

“What had long been considered two different species—one found across a wide swath of Asia and the other a tramp species spread by humans across Europe, Africa, the Americas and Australia—are actually one single supertramp species,” Economo explained. “It is striking that we had these two continental super-common invaders with almost entirely complementary ranges right under our noses, yet until now no one noticed they were actually the same species,”

More information: Sarnat EM, Fischer G, Guénard B, Economo EP (2015) Introduced Pheidole of the world: taxonomy, biology and distribution. ZooKeys 543: 1-109.DOI: 10.3897/zookeys.543.6050

Read more at:

Pheidole flavens-complex introduced to the southwestern Pacific

Here’s the story behind the new Bioinvasions Records article on that just came out. Christian Rabeling and Ed Wilson went to Vanuatu a few years back in 2011 because it was one of the few Melanesian islands that Wilson had never collected from. They collected all the ants they could find in a general survey and kindly sent their Pheidole to the Economo lab at OIST so that I could match them against our other Pacific Pheidole collections and Evan could include them in our phylogenetic analysis. Christian and Ev caught some great Pheidole from the island, including this beautifully spinescent endemic from the sexspinosa complex shown below (CASENT0282641).

An elegant Vanuatu endemic ant species (Pheidole epem198, CASENT0282641) from the Pheidole sexspinosa complex

But one species came out in an unexpected branch on the phylogeny. Instead of coming out with the Old World clade with all the other native Melanesian ants, this one species was reliably nested within the New World clade. It’s closest relatives on the tree were two species that had been included in Corrie Moreau’s 2008 Pheidole phylogeny and id’d as P. moerens and P. flavens–both of which are considered to be invasive.

Major worker of a species from the Pheidole flavens-complex from Espiritu Santo, Vanuatu; collection code CR111110-15, specimen code CASENT0248836. (1) Lateral view, (2) fullface view, (3) dorsal view, (4) hypostomal bridge.

Major worker of a species from the Pheidole flavens-complex from Espiritu Santo, Vanuatu; collection code CR111110-15, specimen code CASENT0248836. (1) Lateral view, (2) fullface view, (3) dorsal view, (4) hypostomal bridge.


Minor worker of a species from the Pheidole flavens-complex from Espiritu Santo, Vanuatu; collection code CR111110-15, specimen code CASENT0248835. (5) Lateral view, (6) fullface view, (7) dorsal view

We wanted to let other researchers know about the spread of this trampy species into the Pacific, so we wrote up a rapid communication article for Bioinvasions Records. The idea was to get the basic information about the new discovery out as quickly as possible, so others in the region could be on the lookout for additional incursions.

The most frustrating part of this study was trying to get a name on the species. Unfortunately, the taxonomy of P. flavens and its close relatives like P. moerens and P. exigua is a super sticky mess, rife with infra-specific names, lost holotypes, and inaccurate determinations. It seems like these taxonomic morasses plague trampy species (like P. flavens and friends) much more often than your average ant species.

Why is it that trampy species so often belong to species-complexes? What are species-complexes, anyways? I suppose I’d define them as geographically distinct populations that are somewhere on the continuum of streching from a recently coalesced species radiation on one end to a network of geographically isolated groups with some low amount of gene flow still persisting. For the taxonomist or even the molecular systematist there is no clear way to know whether to call these things five geographically isolated species or one widespread species.

Whatever the population on Vanuatu turns out to be, it doesn’t match the neotype of P. flavens or the syntypes of P. moerens, so for now we have to settle for calling it a member of the flavens-complex and hope that someone tries to untangle this taxonomic knot in the near future.

EM Sarnat, C Rabeling, EP Economo & EO Wilson (2014) First record of a species from the New World Pheidole flavens-complex (Hymenoptera: Formicidae) introduced to the southwestern Pacific. Bioinvasions Records 3: 301-307. | PDF


How to identify Solenopsis invicta using Antkey

In this tutorial I demonstrate a few different approaches to identifying Solenopsis invicta, also known as the Red Imported Fire Ant (RIFA), using Antkey. The key can be accessed at

How to identify Solenopsis invicta using Antkey from Eli Sarnat on Vimeo.

How to use Antkey’s Lucid3 interactive key

In this tutorial I demonstrate how to make the most effective use of Antkey’s interactive Lucid3 key for identifying invasive and introduced ants. There are tips on how to use features like the ‘best’ and ‘next best’ buttons, what the different panels mean, how to make effective use of thumbnail and pop-up images and how to adjust the text size.

How to use Lucid Key for identifying ants from Eli Sarnat on Vimeo.

Antkey release

Andy Suarez and I are excited to announce the release our project. The project was funded by USDA-APHIS-PPQ-CPHST and the Encyclopedia of Life (EOL) Rubenstein Fellowship program to provide an online identification guide to invasive, introduced and commonly intercepted ants.

Download USDA Antkey Announcement

Frontpage of the site


Over 15,000 species of ants have been described, and more than 200 have established populations outside of their native ranges. A small subset of these have become highly destructive invaders including five which are currently listed among the world’s 100 worst invasive species. Unfortunately, detection of non-native ants is hampered by the taxonomic specialization required for accurate species identification.  Antkey seeks to mitigate the spread of established introduced ants and prevent the incursion of new introductions by providing quarantine personnel, inspectors and conservation biologists with a user-friendly identification resource specifically designed for non-specialists.

Antkey focuses on over 115 ant species that are introduced, invasive or commonly intercepted in North America and the Pacific Islands. Features include an interactive Lucid key, dynamically generated species pages, a searchable media collection of over 1150 images, over 70 live video clips of introduced ants, a fully illustrated glossary with over 400 terms, a searchable database of introduced ant literature, over 12,000 specimen records of introduced ants imported from Antweb (, and community features such as blogs, discussion forums and comment options.

Tabbed species page for Linepithema humile on

The interactive Lucid key allows users to start at multiple entry points, skip ambiguous or difficult characters, and keep track of the choices already made. Novice users can use the ‘best’ feature to determine which available characters will lead to the most parsimonious pathway. More advanced users can skip straight to subfamily or genus. The characters are illustrated with original line drawings and link to glossary definitions and additional specimen photographs.

The Antkey taxonomic classification includes 8 subfamilies, 43 genera and 116 valid species. Taxon pages include tabs for overview, descriptions, media, maps, literature and specimens. In addition to original diagnostic descriptions and overview sections, all the species pages dynamically import relevant articles from the Encyclopedia of Life ( and specimen images from Antweb. The Google maps are dynamically generated from specimen data imported from Antweb and distribution data imported from GBIF.

The media feature contains over 1150 images and uses a faceted search tool that allows users to filter images by media gallery, taxonomic name, keywords, description and creator. Each thumbnail links to a lightbox window that displays the standard scaled image and associated metadata, and also offers a link to download the original, full-sized image. All images tagged with a taxon name automatically appear on that taxon’s species page.

Media feature in Antkey allows users to filter their searches based on morphological terms, taxonomic names, image type, media galleries and keywords.

The site includes approximately 75 video clips of 22 species. There are many important identification characters for ant species that are only possible to detect while the ant is alive. The standardized thirty-second video clips feature ants feeding at and recruiting to baits, foraging in natural environments, and entering and exiting their nests. The videos can be downloaded by users or embedded in other webpages.

A fully illustrated glossary of over 400 terms, including all the character states used in the Lucid key, allows users to quickly learn the important morphology needed to make accurate identifications. The terms are integrated throughout the site so that whenever one appears in the text the user can point to it and the definition will automatically display.

One of the greatest strengths of Antkey is that it was developed using the Scratchpads platform.  Scratchpads ( is a social networking platform that allows communities to bring taxonomic information together without the limitations of traditional paper-based publications. Web systems and content can be developed and updated in minutes so websites can reflect the latest knowledge of a particular group. The platform also allows multiple authors to create and edit content without using any html code. The Scratchpads platform relies on the content management system Drupal ( for its underlying architecture.

Introduced Nylanderia of the United States

I’ve spent the last couple of days parsing the differences among the many introduced species of Nylanderia. I still haven’t gotten a good look at the Rasperry Crazy Ant or Caribbean Crazy Ant or the Hairy Crazy Ant or whatever folks are calling the species that has been spreading across the southeastern United States, but apparently it is close to N. fulva and N. pubens. Hopefully John LaPolla’s revision of the Nearctic Nylanderia will be out soon, and I’ll be able to update my provincial key characters.

In the meantime, here’s a link to an illustrated comparison chart of Nylanderia introduced to the United States (including Hawaii).

And here’s a gallery of the various illustrations I’ve put together thus far for the key.

Selected references and resources of introduced Nylanderia species. (Note that all these species of Nylanderia were treated as Paratrechina prior to LaPolla et al. (2010)).

Trager, J.C. (1984) A revision of the genus Paratrechina (Hymenoptera: Formicidae) of the continental United States. Sociobiology, 9, 49-162. [Includes keys and descriptions of N. bourbonica, N. flavipes, N. guatemalensis, N. fulva, N. vividula all in addition to the native species].

LaPolla, J. S.; Hawkes, P. G.; Fisher, B. L. 2011. Monograph of Nylanderia (Hymenoptera: Formicidae) of the World, Part I: Nylanderia in the Afrotropics. Zootaxa 3110:10-36. [PDF] [Covers three spp. of Nylanderia purportedly introduced to the Afrotropics, including N. bourbonica, N. vaga and N. vividula.]

LaPolla, J.S., Brady, S.G. & Shattuck, S.O. (2010) Phylogeny and taxonomy of the Prenolepis genus-group of ants (Hymenoptera: Formicidae). Syst. Entomol., 35, 118-131. [PDF]

Ivanov, K. & Milligan, J. (2006) Paratrechina flavipes (Smith) (Hymenoptera: Formicidae), a new exotic ant for Ohio. Proc. Entomol. Soc. Washington, 110, 439-444. [Nice small paper on N. flavipes and how to distinguish it from N. vividula.]

Ants of the Southeastern United States – key to species of Nylanderia. [Excellent website of Joe MacGown with a key adapted from Trager (1984).]

Illustrating ant hairs


One of the most satisfying things to do when illustrating ants with Adobe Illustrator (AI) is to turn rather dull hairs into elegant tapered masterpieces. Hairs, or ‘setae’ as the traditionalists prefer, can be excellent characters for identification. For my introduced ant key, I need to come up with characters for distinguishing Camponotus planatus from Camponotus atriceps. I’ve coded both as having abundant long erect hairs on the head, mesosoma and gaster. But the quality of the hairs is different between these two. Those of C. planatus are stiff and thick, while those of C. atriceps are slender and flexuous. Here’s a quick post on how I drew the hairs for C. atriceps.


First thing was to import a photograph of C. atriceps from Antweb. I had to rotate it to the standard position where the back two coxae are level with each other.

Screenshot of Adobe Illustrator with specimen photo of C. atricpes placed as the first layer.


Next I created new layers for the head, mesosoma, waist and gaster, and drew the outlines using the Pen tool. I hope to post more on these basic steps of tracing specimen images in the near future.

The outlines of the specimen have been traced with the pen tool, and filled in with white.


Now I create a new layer for the hairs, and lock all of the other layers.

New 'hairs' layer is created and I zoom in a bit.


The next step is to trace the hairs. There are a few ways to do this, but the trick is to achieve a nice smooth curve. With hairs, I like to use the Pencil tool and trace on my x200 Thinkpad tablet. Before I had my tablet, though, I would probably stick with the Pen tool for these type of long flexuous hairs. If you do opt for the Pencil tool, make sure to double click on it and select a nice smoothness (I used 75%) and get rid of the ‘edit paths’ option for sure.


Hairs are traced using the Pencil tool with a tablet, but the Pen tool works well for these as well.

Once I’ve traced all the hairs on the profile outline, I hide the specimen photograph layer to see how it looks.


Here comes the cool part: making a new hair type.

  1. Use the pen tool to draw a straight line approximately as long as one of the longer hairs. Change the stroke to 0.25.
  2. Select the line and copy it (Control+C).
  3. Paste the line to the back (Control+B). This pastes the copy directly behind the original.
  4. Use the ‘Direct Select’ tool (A) and drag a selection box around the top two points (it looks like just one point because the copy is directly behind the original). Now join the two selected points. I do this by right clicking and selecting ‘Join’, but I’m sure there are other ways to get there.
  5. Again using the Direct Select tool, click on one of the bottom points. Use the arrow keys to move it a few pixels to the left. I changed the default keyboard increment (Edit > Preferences > General) to .001 in to have a bit more precision.
  6. Now select the other bottom point and move it an equal number of spaces to the right.
  7. Draw a line joining these two bottom points.
  8. Use the ‘Add anchor point’ tool (+) to drop an anchor point in the middle of this bottom line.
  9. Select the middle anchor point and move it down a few spaces. Click it and hold with the ‘Convert anchor points’ tool (Shift+C) to add a little curve to the bottom line.
  10. Fill the resulting polygon with black (or you could go for a gray if they are very light hairs if you want).
  11. Use the regular Selection tool (V) to select the whole object.
  12. Open the ‘Brushes’ window and create a new brush (lower right page icon in the window). Make it an Art Brush.
  13. Name the brush, and make sure the arrow is pointing upwards towards the pointy end (so long as you drew the hairs from the base to the tip). Save the brush library as ‘Ant Hairs’ or something like that. Sometimes if the following steps don’t work, I copy my hair to a new AI window and make a new brush. Some odd glitch or something, but sometimes it doesn’t save the brush correctly.
  14. Now select all your hairs. Easy way to do this is to make sure all the other layers are locked except for the hair layer, then do a ‘Select All’ command (Control+A). Click the new hair brush on the brush panel window, and voila. If the hairs are backwards, you may need to switch the way the arrow points in the brush options.

Lines rendered as hairs using my new C. atriceps hairs brush. Notice the fine tapering!


Now that you have the hair brush, you can paint hairs directly using the paintbrush tool. I find the paintbrush tool takes a lot longer, though, so I personally prefer using the pen or pencil tool, and then selecting all the strokes and converting them to brushstrokes with whichever ant hairs brush best suites the job.

Trampy Linepithema

As I am developing the new update to my Lucid key to invasive ants, I realized it might be a good idea to post some of the illustrations I’m working on as little vignettes of the larger project. When I’m not quite sure about an ant ID, I find myself using the ‘comparison chart’ tab on PIAkey more often than the actual Lucid key. It’s like a quick-access cheat sheet for when you already know the genus and just need a little refresher for distinguishing among a few species.

This chart shows how to tell the very commonly encountered Argentine ant (Linepithema humile) from its less well known, but occasionally intercepted congener L. iniquum. The characters are adapted from Alex Wild’s treatise of the genus (Wild, 2007).

L. humileL. iniquum
Erect hairs on cephalic dorsum (above eye level) + gastral tergites 1 & 2



Dense pubescence covering mesopleura



number of convexities on profile of mesosomal dorsum



propodeal shape



propodeal spiracle bordering posterior margin of propodeal profile




Introduced Ants and POE Ants now on Antweb

Two new projects recently went live on Antweb that are aimed at helping folks identify the ever-growing cadre of invasive, introduced and intercepted ants.

The Introduced Ants project lists 157 species (136 imaged) that have established populations outside of their native range. The project is being curated by Brian Fisher, Andrew Suarez and myself.

“Of the nearly 14,000 described species of ants, over 200 have established populations outside of their native range. Some of these have become highly destructive invaders. In addition to being economically costly in both urban and agricultural areas, invasive ants can modify ecosystems by reducing native ant diversity, negatively affect vertebrate populations, and disrupt ant-plant mutualisms. However, for most introduced ants we know little about their impacts and less about their biology; we often don’t even know where they are from. The goals of the introduced ant page on is to collate information on where introduced ants are found, and help provide taxonomic resources for introduced ants. Ultimately, we hope this site will provide information on 1) biogeographic patterns of invasion including the identification of regions that may either produce many invaders or be particularly prone to invasion, and 2) taxonomic perspectives on invasion success. Here we provide a list of introduced ants, that is those ants known to have established populations outside their native range. A far greater number of species have been intercepted at ports of entry but have not become established (see Port of Entry ants).” – Antweb

The Port of Entry Ants project is being curated by Andy Suarez and myself, and is composed of 210 species (192 imaged) that have been intercepted at United States ports of entry. The baseline of this project are the USNM specimens Suarez and Ward (2005) identified to examine the role of opportunity in the unintentional introduction of nonnative ants. Andrea Walked (Suarez Lab, UIUC) has done an excellent job with the imaging, and Michele Esposito (CAS) has helped with the data handling. Hopefully this project will expand to include ants intercepted on an international scale.

Biological invasions are a leading threat to biodiversity, agriculture and the economy. Ants are among the most damaging introduced species, yet we know very little about why some ant species become successful invaders. A major challenge of invasion biology lies in the development of a predictive understanding of invasion processes. However, this is inherently difficult because different characteristics may be important for different species or during different stages of invasion. Subsequently, research on invasive ants needs to examine taxonomic patterns across each of the three distinct stages of invasion: opportunity, establishment and spread.

“To examine the role of opportunity in invasion, we are developing a database of ants intercepted in quarantine worldwide. These data will be used to examine why some species succeed as invaders while others do not. Surprisingly, there is a remarkable diversity of ant species moving around the world as a result of human commerce. However, relatively few species become established suggesting that opportunity alone is insufficient for introduced species to establish and spread.” – Antweb