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This struck a chord in part because we get them occasionally at this
time of year too, nearer the end of August on what's left of our lawn
in Halifax.
Another interesting thing about these female P. polyturator is the
extreme enlargement of the tibia of the two long hind legs. The
proximal end of this part of each of the 6 legs in most insects
contains a multi-sensor ground vibration detector called the subgenual
organ, SGO ('below-the-knee organ'). It's sensitive to displacements
down to about 1 nanometer in a cockroach (with its 25 sensors), about
the same as the displacement at the basilar membrane inside the
cochlea of the ear at absolute sound threshold at our best frequency;
the threshold there is probably limited by Brownian motion of
particles in the fluid bombarding the membrane.
It's possible that the extreme enlargement in the metathoracic tibiae
of Pelecinus represents some even greater enhancement, perhaps in
low-frequency tuning or averaging using its SGO. That could help the
wasp detect the specific vibrations produced by its June Bug larval
targets that apparently live several centimeters underground. Years
ago I made a couple of tibial preparations and sent them to a German
academic who had expressed an interest in doing the necessary
electron-microscopy, but as far as I know this was a minor wasted
effort as he never followed through on it. Interests diverge and
progress, so such cul-de-sacs are not unknown in science.
Steve, Halifax
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Quoting Christopher Majka <c.majka@ns.sympatico.ca>:
> Hi Jim,
> They are a fabulous beast. It is certainly Pelecinus polyturator,
> since this is a mono-specific genus. Males are occasionally found in
> southern latitudes, but in the Maritimes it is an exclusively
> parthenogenically-reproducing female species.
>
> Cheers,
>
> Chris
>
> On 7-Aug-11, at 8:09 PM, James W. Wolford wrote:
>
>> AUGUST 5 & 6, 2011 - Pat & I drove to Lunenburg for 2 of the
>> 3.5-day Folk Harbour Festival.
>>
>> On our first afternoon there, on the lawn behind the Lincoln House
>> ex-B&B, we found a very-long-bodied female Pelecinidae black wasp
>> that hunts and preys on grubs/larvae of May beetles or June beetles
>> under the sod. Very probably this was a Pelecinus polyturator ,
>> which exists as nearly all females in most or all areas of
>> occurrence. The species has a wide range in North America and
>> apparently exists under several different names. Since they are
>> nearly all females, the eggs they lay, one at a time on each beetle
>> larva found, must be parthenogenic, i.e. not needing
>> fertilization, and probably formed by a modified form of meiosis.
>>
>> Cheers from Jim in Wolfville.
>
> Christopher Majka <c.majka@ns.sympatico.ca> | Halifax, Nova Scotia, Canada
>
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