Ants in Korea
I caught an interesting article from BBC Earth News last night that involves a study of 'super-colonies' among Linepithema humile (Argentine ants). The general idea behind the report is that transplanted ants from the Paraná River basin have set up massive-sized colonies stretching along the coasts of the Mediterranean (6,000km), southern California (900km), and western Japan. These ants all share a common genetic make-up, which means that groups from neighboring sites do not attack one another as they would within other ant populations. In particular, the chemical make-up of hydrocarbons on the ants' cuticles seems to hold the key in recognizing friend from foe.
According to the BBC piece, representatives from all of the super-colonies "rubbed antennae with one another and never became aggressive or tried to avoid one another". Meanwhile, those from 'smaller' colonies (in Catalonia, Spain and Kobe, Japan) were very aggressive toward their colonial brethren -- the ants taken from the super-colonies of the Mediterranean and western Japan. And what does "very aggressive" mean? Well, the San Diego Union-Tribune has a piece on Argentine ants that mentions research conducted by David Holway, Andrew V. Suarez, et al. and includes the following:
At territorial boundaries where ants of different colonies confront each other, full-fledged battles are frequent, murderous and epic on a miniature scale.
During one six-month study, for example, Thomas [Melissa Thomas, a University of California-San Diego postdoctoral fellow involved with the study] estimated that border skirmishes around one of the smaller colonies at Lake Hodges resulted in the deaths of at least 15 million workers.
Well crap. You can read or download a .pdf file of Thomas' paper (When supercolonies collide: territorial aggression in an invasive and unicolonial social insect) for further information on where her figures come from. I'm a little concerned about the different colonies in Japan, as it may only be a matter of time before individuals are transplanted to Korea and effect ecosystems here. Their presence in southern California has led to a 50% decline in the Coastal Horned Lizard population, and has an even greater impact lower on the food chain:
As long as there is significant outside competition, Argentine ants are protein-hungry carnivores, feeding on the blood of native ants and other insects. But as their competitors (and primary food source) begin to dwindle in number, Argentine ants switch to a carbohydrate-rich, sugary diet of honeydew nectar - digested plant sap excreted by aphids and scales. It's the sticky stuff you sometimes find on your car windshield after you park beneath a tree, said Holway.
Kill and eat your competition until they're extirpated then switch to feeding from - and protecting - known plant pests. Oh yeah, sounds great to me, too.
Current pest control measures have focused on altering hydrocarbon chains on the ant's exoskeleton so that nest-mates mistake returning workers for outside invaders. Guess it's hard for a colony to grow when its foragers keep getting torn to bits. However, Argentine ant colonies typically have several queens, so it will be interesting to see how effective this is in the long run. Some of the articles I've come across are a couple of years old, but without access to academic journals it's hard to tell what's going on now.
Camponotus japonicus by autan
The Korean word for ant is 개미 and there are eight species listed in my guidebook to Korean insects.
Crematogaster brunnea (검정꼬리치개미) - a type of acrobat ant. No common name found.
Camponotus japonicus (일본왕개미) - a type of carpenter ant. No common name found. ("Japanese King Ant"?)
Formica japonica (곰개미) - a type of wood ant. No common name found. (Bear Ant?)
Lasius niger (고동털개미) - a type of formicine ant. Black garden ant. (something-Hair Ant?)
Monomorium pharaonis (애집개미) - Pharaoh ant. (something-House Ant?)
Polyrhachis lamellidens (가시개미) - a type of black ant. No common name found. (Thorn Ant?) Medical uses in China
Pristomyrmex japonicus (그물등개미) - a type of queenless ant. No common name found. (something-Mesh/Net Ant?)
Tetramorium caespitum (주름개미) - Pavement ant. (Pleated/Wrinkled Ant?)