A mysterious crazy ant

Nylanderia fulva (Credit: Alex Wild)

The Rasberry Crazy Ant is an invasive ant in North America that was first noticed infesting areas around Houston, Texas about ten years ago, but its species identity has remained undetermined until now.

Ants of the 'crazy ant' species complex got their name because of the ants' random, nonlinear movements. This particular species was called "Rasberry" after the exterminator Tom Rasberry who first noticed the ants were a problem in 2002. This species is able to out-compete fire ants because they reproduce faster. They are not attracted to ordinary ant baits, cannot be controlled by over-the-counter pesticides, and are harder to fully exterminate because their colonies have multiple queens. But what's the problem? Well, they are infesting electrical equipment which can cause short circuits when they chew through insulation. Overheating and mechanical failures are other problems caused by high numbers of dead worker ants in electrical devices. They were attracted by a pheromone released by a dying ant which signals potential danger by attackers.

Previous attempts at identifying this species have resulted in widely different conclusions with respect to its native range, source, and biology, let alone its species name. A new study identified the invader as Nylanderia fulva by using morphometric data, molecular sequence data  from six independent loci, one being COI, and more traditional morphological comparisons with type specimens. Previous attempts at identification using DNA Barcoding and morphometric analyses could not exclude closely related species but placed it with a closely related sister species. A good example for the fact that a DNA Barcode is not the all-encompassing miracle tool - nobody ever claimed that - but rather one of many in an integrated framework available to modern biology. Even more so because now with the knowledge of the species identity the search for some single diagnostic characters in the COI sequence can begin.

The researchers were also able to document the utility of the new knowledge. They could show that the species  is distributed more widely than previously thought and has likely invaded all Gulf Coast states. "This study demonstrates the invaluable role that taxonomy, an often underappreciated discipline, plays in our understanding of emerging pests. Now that we know just what species the Rasberry Crazy Ant really is, we can better understand its biology to improve control of this invasive species", says John LaPolla, one of the authors of the study.