Yes, much more entertaining than television! :-)
RB>They have no caution whatsoever; I guess the figure "hey,
RB>I'm a yellowjacket, who's going to bother me?"
I've noticed the same thing and observed the following behavior as well:
Ants are caught because of sheer weight of numbers. Most ants who visit
a pitcher, if not the vast majority, feed and leave unharmed (if they
didn't fill up and leave before being caught, they couldn't return to
the nest and let the others know about the food source and encourage
them to come too). This constant stream of returning ants keeps the
chemical trail fresh and keeps more ants coming. If you have a pitcher
being visited by ants, you'll notice the number of ants leaving it is
almost identical to the number coming up the trail to the mouth of the
pitcher. Most ants begin feeding at the first source of nectar they
come upon, fill up and leave. A few walk over their feeding sisters,
stumble out onto the danger zone and fall in. This tiny fraction of the
visiting ants, because of the huge numbers involved, soon builds up to a
point where it can easily fill up an entire pitcher. The majority of
the colony's members return home safely with food, probably individuals
even make multiple safe trips. The plant also gets pitchers full of
food, it seems both sides benefit from the exchange.
Flies usually land on the side of the pitcher or on the hood. They walk
up the pitcher, if they come across a nectar-covered pitcher wing their
mouthparts drop down and they settle a while, but it's usually not
enough to satisfy them. They soon crawl up to the mouth of the pitcher.
If they land on the hood they'll feed on the nectar on the underside and
work their way down, sometimes they'll just settle on the top of the
hood and sun themselves there for a while. :-) They can usually feed
safely on the rim or the underside of the hood but flies are very
agitated and don't like to stand still for long while feeding. Either
they'll fly off at this point or enter the danger zone, first leaving 2
pairs, then one pair, finally only a single leg on the rim while they
feed further down the throat of the pitcher. Then the last leg enters
the pitcher as well. A few more steps down and suddenly the fly loses
its footing. Many times it recovers and flies out of the pitcher in
mid-drop. This might be enough to make it leave but some just land on
the pitcher or hood and start the process all over again. I once saw a
horsefly do the mid-drop recovery 5 times, on the 6th drop he began
flapping his wings just a millisecond too late to make his escape and
was finally caught. The most dangerous surface for a fly is the area of
the pitcher right beneath the base of the hood, if a fly walks headfirst
from the underside of the hood onto this area there's no rim for it to
grab onto and it quickly loses its hold on the wall. The smell of
decaying prey probably serves as a fly attractant as well, I notice the
amount of flies around a pitcher increases as it gets older.
Yellow jackets rarely land on the hoods or pitcher bodies of my upright
Sarracenia, they hover around the mouth a few seconds, sometimes land on
the rim, but always if they do they immediately go headfirst into the
pitcher tube without pausing. Usually they don't even do this much, but
simply fly at full speed straight down the throats of the pitchers, what
I call "dive bombing". They only seem to walk alot on the surfaces of
my S. psittacina, it must be the angle of the entrance, they land in the
center of the rosette, walk up a pitcher and enter the hood. At first I
didn't think the angle of the pitchers would be enough to hold them very
well, but when I opened up psittacina traps at the end of the season
they were filled with closely packed yellow jacket bodies so they are in
fact quite successful.
Nope, we aren't kidding when we call these plants carnivorous! :-)
Regards,
Demetrios