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From: kaufman@maxzilla.Encore.COM (Lar Kaufman)
Newsgroups: sci.bio
Subject: Re: Ants and antagonists
Message-ID: <4590@xenna.Encore.COM>
Date: 5 Jan 89 23:40:05 GMT
References: <18762@agate.BERKELEY.EDU>
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Reply-To: kaufman@maxzilla.UUCP (Lar Kaufman)
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In article <18762@agate.BERKELEY.EDU> bks@ALFA.berkeley.edu ( Brad Sherman ) writes:
>The Megalopolis stretching some 50 miles from Sacramento to the
>San Francisco Bay Area is currently undergoing an invasion of
>(so-called Argentinian) ants.
>	1) What is the probable cause of this phenomenon?
Probable cause is the introduction of a foreign species by human
vector. Most likely brought in with foodstuffs. No adequate natural
control, as you noted (next).

>	2) With no indigenous anteaters, is available food the
>	only limiting factor to the ant population? (This seems
>	unlikely). 
Native competition may or may not suffice to control them. Probably
not. Other opportunistic predators might increase in population at the
unexpected increase in ant supply. Probably not. More likely scenario
- The "fire ant" introduced in the southeast (is this the same ant?)
some time ago, has spread throughout the southeast until contained by
one of two factors: lack of adequate heat, and lack of adequate
moisture. The fire ant has spread north above the Mason-Dixon line in
places, I think. It cannot take really cold weather, but pockets of
them have dug in around building foundations and such well to the
north of their otherwise maximum northern range - they just need a
certain minimum temperature for their winter "diggings." 
  The fire ants' westward expansion was stopped at the desert
southwest. If these are the same ants as the Argentinian ants you are
describing, someone has helped them across the barrier - probably by
transferring eggs in a quantity of dirt. You can then expect them to
expand eastward and northward. The barriers to further expansion
wouldn't necessarily be cold and aridity; they could be altitude and
wetness, for example. 
   Attempts to hold the line on the fire ant failed miserably. They
can be eradicated in isolated areas by topical application of
Amdro(tm) a pesticide that has unfortunate consequences for fishes and
some other critters. 

  [ stuff I can't respond to, deleted ]
>
>Sorry if this is this question is inappropriate for this group,
>but there doesn't seem to be a sci.naturalhistory.
It sounds like this would have fit nicely in the proposed
sci.environment group. Voting is going on now, I think.
 
  -lar
 Lar Kaufman   <= my opinions          Fidonet: 1:322/470@508-534-1842 
 kaufman@multimax.arpa    {bu-cs,decvax,necntc,talcott}!encore!kaufman