18 replies to this topic

[kalimant]

Looks like what's his name may have been correct? I didn't read his posts or look at the timeline, but there was a 100+ ha infestation in San Diego after the 2014 one, which was much smaller.

 

That large an area (about 1 sq km) means they pushed away all the Linepithema humile ants outside of it.

 

https://escholarship...c/item/2b1813r9

 

The big-headed ant, Pheidole megacephala, is an ecologically destructive invader of tropical and subtropical environments worldwide. In April 2014, an established infestation of P. megacephala was discovered in a residential neighborhood in Costa Mesa, Orange County, and a second infestation was found in a residential neighborhood in San Diego, San Diego County, in 2019. Although big-headed ants are regularly detected in commerce in California, the records from Costa Mesa and San Diego represent the first established infestations known from the state. To learn more about the distribution of P. megacephala in California and to assess its potential for further spread, we delineated both known infestations and compared this species to another widespread invader, the Argentine ant (Linepithema humile), with respect to desiccation tolerance and resource assimilation (δ15N). Both known P. megacephala infestations extend over multiple hectares of suburban development, with the San Diego infestation exceeding 100 ha and the Costa Mesa infestation exceeding 10 ha. Both infestations are spatially continuous and encompassed by established populations of the Argentine ant. The big-headed ant overlapped broadly with the Argentine ant both in terms of desiccation tolerance and δ15N values. These similarities suggest that the big-headed ant could continue to spread in urban environments in coastal southern California and cause impacts comparable to those resulting from invasion by the Argentine ant.

Edited by kalimant, September 9 2024 - 9:03 AM.

[bmb1bee]

Terrifying...

[ANTdrew]

Vendayn’s vindication.

[gcsnelling]

Not a shock, I figured once I found them in Costa Mesa, they would turn up in other places. It sucks though not to be able to read the entire thing.

Edited by gcsnelling, September 9 2024 - 2:21 PM.

[mbullock42086]

they have been here since 2010 or so, noticed them around 2013-ish.  

  all over anaheim because everyone uses rock gardens there

[gcsnelling]

Considering  the extent of the CM population that time line makes sense.

[kalimant]

Not a shock, I figured once I found them in Costa Mesa, they would turn up in other places. It sucks though not to be able to read the entire thing.

 

Based on this recent pdf, it looks like California considers them established, and that eradication is now not possible.

 

https://blogs.cdfa.c...megacephala.pdf
 

Pheidole megacephala is an ant that appears to have potential for economic and environmental impacts in California. It is established in two counties and eradication does not appear feasible. For these reasons, a “B” rating is justified. 

 

I have a feeling it'll like the environment there...not so heavy rain plus lots of irrigated water. Low humidity and temp will hinder it beyond the suburbs and urban areas though. 

Edited by kalimant, September 9 2024 - 5:00 PM.

[gcsnelling]

That's how I read it as well.

[ReignofRage]

It doesn't exactly read that they "pushed away all the Linepithema humile ants outside of it," considering they state that the infestation zones are "... spatially continuous and encompassed by established populations of the Argentine ant." I'm just wondering when they'll figure out they they've been in Los Angeles for a while now. 

[kalimant]

It doesn't exactly read that they "pushed away all the Linepithema humile ants outside of it," considering they state that the infestation zones are "... spatially continuous and encompassed by established populations of the Argentine ant." I'm just wondering when they'll figure out they they've been in Los Angeles for a while now. 

 

I take "continuous" to mean that the P. megacephala samples are clustered as a single, non-disjunct group, and that this cluster is surrounded (or "encompassed") by L. humile ants. This would be par for the course for all the large P. megacephala clusters that I've seen, where they tend to exclude aggressive strong mass recruiting competitors from their core territory.

 

Also, so you've seen P. megacephala in LA?

Edited by kalimant, September 10 2024 - 2:08 AM.

[RedFox]

Dang I have a colony of P. megacephala here in Michigan, I have them in a natural setup. I didn't know they were this invasive, they were a gift. I've had them for 3 months and they have exploded in numbers. I do have them well contained.

[gcsnelling]

I'm just wondering when they'll figure out they they've been in Los Angeles for a while now. 

Don't hold your breath.

[mbullock42086]

it would actually be really cool if megacephala ended up wiping out the argentine ants in socal and did little damage ecologically lol

[eea]

it would actually be really cool if megacephala ended up wiping out the argentine ants in socal and did little damage ecologically lol

I hope so too, they look way more interesting than Argentine ants.

[mbullock42086]

 

it would actually be really cool if megacephala ended up wiping out the argentine ants in socal and did little damage ecologically lol

I hope so too, they look way more interesting than Argentine ants.

 

  and they're not likely to destroy an entire room of specimens as opposed to argentine ants.  when megacephala invaded my home it was a little cute foraging trail and they just wanted a piece of granola lol. only did it once, and they never came back. i freaked out at first because they gave me pharaoh ant and S molesta flashbacks but saw a a major and felt relief.

[ReignofRage]

I take "continuous" to mean that the P. megacephala samples are clustered as a single, non-disjunct group, and that this cluster is surrounded (or "encompassed") by L. humile ants. This would be par for the course for all the large P. megacephala clusters that I've seen, where they tend to exclude aggressive strong mass recruiting competitors from their core territory.

 

Also, so you've seen P. megacephala in LA?

 

 

I have observed both P. megacephala and P. fervens in the Los Angeles area - the latter seeming to be a non-issue species. From my observations, the populations of P. megacephala are mixed with Linepithema humile here in California.

[kalimant]

 

I take "continuous" to mean that the P. megacephala samples are clustered as a single, non-disjunct group, and that this cluster is surrounded (or "encompassed") by L. humile ants. This would be par for the course for all the large P. megacephala clusters that I've seen, where they tend to exclude aggressive strong mass recruiting competitors from their core territory.

 

Also, so you've seen P. megacephala in LA?

 

 

I have observed both P. megacephala and P. fervens in the Los Angeles area - the latter seeming to be a non-issue species. From my observations, the populations of P. megacephala are mixed with Linepithema humile here in California.

 

 

Interesting on it being in LA and the state not knowing about it. Guess it def is established then.

 

And interesting about the fact they are mixed in with L. humile, which might indicate they are relatively new to the area, and still small in population size. Once the cluster reaches large sizes, the core of their territory usually is bereft of other aggressive mass recruiting ant species. 

 

Would be cool to track and record their expansion over time (or contraction/stable state). Is the climate and other abiotic factors friendly enough that they will out compete L. humile (as in the lowlands of Hawaii for example) and form large territories, or is the California environment more friendly to L. humile instead? I have a feeling it's the latter, but will be happy if that's wrong. 

[ReignofRage]

I do think the weather is more in favor of L. humile; there is a case of the only known established population of Pheidole indica in California being extirpated over a single winter due to it being cooler and wetter than usual, which allowed L. humile to dominate. I do believe the populations of Pheidole fervens in California to be sparse and moving "frequently" due to the winter season allowing L. humile to prove dominant. There is plenty of long-established exotics in urbanized California that live side-by-side with L. humile, so it's somewhat disagreeable, in my experience, to say they will drive out other exotics if given time. Dr. Holway reached out to me about Pheidole megacephala recently, so I can ask him about his theories on it!

[kalimant]

I do think the weather is more in favor of L. humile; there is a case of the only known established population of Pheidole indica in California being extirpated over a single winter due to it being cooler and wetter than usual, which allowed L. humile to dominate. I do believe the populations of Pheidole fervens in California to be sparse and moving "frequently" due to the winter season allowing L. humile to prove dominant. There is plenty of long-established exotics in urbanized California that live side-by-side with L. humile, so it's somewhat disagreeable, in my experience, to say they will drive out other exotics if given time. Dr. Holway reached out to me about Pheidole megacephala recently, so I can ask him about his theories on it!

 

Cooler and wetter environments will definitely not be good towards P. megacephala. Here in FL, I am seeing contraction of a nearby cluster due to the very wet recent weather, where RIFA has reclaimed areas taken by them after continuous rainy days. Does not help that the water table here is so high and we get flooding. In general, the literature also backs up the claim that rainy season pushes back P. megacephala.

Pheidole is also generally a warm weather group, so no surprises about P. fervens and P. indica not doing as well there if it cools.