Here is an ant carrying away a dead bee.
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Here is a pic of my pail feeder with a little branch of walnut leaves beside it.
Click to enlarge!
The ant in that picture there is probably Camponotus pennsylvanicus, they nest in dead wood usually suffering from extreme water damage. Because of their large size and the limited nesting available they usually branch off into smaller sub-colonies, but still only one Queen. (sometimes there can be more but this is short lived.) They probably steal some honey off and on but colonies don't usually get more than 10,000 to 15,000 ants. They focus on more sugary foods in the fall time as it stores better. Usually they have herds of aphids out in the woods. Foraging is mostly done at night.
I've had other species such as Camponotus nearcticus which is half the size of most Camponotus living in my older hive boxes and I've found them in hive attics also. They weaken the wood so I'm switching over to Polystyrene hives. Colonies probably don't grow to much larger than 5,000 ants.
Crematogaster are smaller ants that nest similar to C. pennsylvanicus. They will burrow through the wood and probably steal some honey and pollen too. Probably not something you want in any of your hives. I had to coat the legs of a table my hive sits on with Vegetable Oil and greasy stuff to get them to move out.
http://www.myrmecos.net/myrmicinae/crematogaster.htmlNotice the heart shaped abdomen and scorpion like posture. Species of this genus tend to produce irritating chemicals and odors.
The ants in question in the main post could be a few things depending on where they're from. Up north where it's still cold out it's likely Prenolepis imparis is probably the only ant that can forage during winter months. I have found them marching into my hives but they're only after the honey and are awful predators. It doesn't take much to feed them either. A cell of honey can easily feed a few hundred of their workers. Workers are easily identified because they balloon up with honey.
http://img.photobucket.com/albums/v735/mrilovetheants/P.jpgDown south where it's gotten warmer or never chilled I would say it's more likely a Lasius, or Formica. Formica are slightly smaller ants than the huge Camponotus but they live in the soil. Formica are probably the biggest threat as some species form massive colonies that will over run weak hives. This is seen more out in the woods when a bear has riped open a tree or something like that, these are the ants that would invade the hive afterward. Out in the field however colonies don't get nearly this big. Smaller species tend to do way better at over powering bigger ants but smaller ones are less of a threat to bees. If their nest is nothing more than a small mound or two you don't need to worry.
And obviously if they're fire ants you'd know it from the blistering stings. Fire ants are still a tropical species and only found in southern states.
Solenopsis invicta if anyone's interested.
http://www.myrmecos.net/myrmicinae/solenopsis.html[EDIT] Since you're in LA they could also be harvester ants but without a picture who knows.
http://www.myrmecos.net/myrmicinae/pogonomyrmex.html
