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Science Forum Index » Engineering - Lighting Forum » Light and insects...
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| I.N. Galidakis... |
 Posted: Fri Jun 20, 2008 6:23 pm |
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Continuing a discussion which popped up a while ago, about insects and light:
Two days ago I was required to do several tests to determine whether several
diamonds were fake or not. One of the tests was a UV test.
After I finished the other tests, I fired up my PHILIPS HPW 125W blacklight
mercury vapor. The test was concluded after I placed the diamonds close to the
HPW arc and saw whether they fluoresced bright blue.
Half an hour after I finished, my eye's corner caught the movement of a huge
roach, around 2 inches long, running in the living room.
After I killed it, I was thinking about that statement: "Roaches avoid light".
It is true that large roaches avoid light sources and hide in dark corners, but
apparently they do get attracted by mercury vapor lamps.
On the HPW lamp, the Wood's glass filter blocks the 435.8 nm line completely and
allows only the 405-407 lines through, plus most of the long UV lines, down to
the 365nm line.
My mother's windows were almost completely shut and only the drapes fluoresced.
However, as soon as the lamp was fired, the little guest found its way in after
a while.
Roaches here are different than those in the States. Here they fly. They are the
Vlatta Periplanetta Americana, kind, whereas I think in the States, most city
roaches are either Vlatta Germanica or otherwise wingless.
They congregate in thousands in the city sewers and rarely visit the surface,
except on very hot, humid days.
In order for a roach to make it into the first floor apartment (1st floor
Europe=2nd floor States), it would have to have been flying already, prior to
seeing the 365nm light and then it would have to have changed its direction and
come and land onto one of the two window sills which were semi-open, before it
got in.
A similar incident I remember back in 1982, when I was living in a different
apartment: Back then I had installed high pressure mercury vapor fluorescent
lamps on my mother's first floor balcony and people were always commenting "what
kind of wonderful lighting is this?"
One friend who was living in a penthouse next door, asked me if I knew how he
could install similar "wonderful" lights. I offered to install them myself, if
he could only pay for the materials. He agreed. Then, we spent the next two days
buying ballasts and lamps and rewiring the open space around the penthouse.
After about 2-3 days of work, he finally displayed proudly all his mercury
lights on the 7-th floor penthouse. The penthouse balcony was illuminated by 6 x
125W Tungsram mercury fluorescent lamps. From below it looked fantastic. I
imagine it looked so from above as well, but I could not tell, because our
apartment was on the first floor.
The penthouse owner was one happy camper. He kept telling me how nice they
looked and he had them on every night for two weeks. Then, one day he stopped
using them.
After about a month I asked him what was the deal and why he stopped lighting
the place. He said: "It was like a nightmare! We had several visitors the other
night and we were enjoying our drinks. When the guests sat up ready to leave,
one of the ladies had three huge roaches on the back of her dress, and the other
lady had two on her hair. They were _large_ beasts... I un-installed the
lamps...."
These beasts appear able to see the spectrum from 365nm to 400nm and they will
gladly "zoom in" whenever they see an appropriate source. I am aware that
insects can see in the UV some, but I wonder what the purpose for this
specialized roach vision is, because large roaches here dwell in sewers, where
there is absolutely no need for such light.
Fascinating creatures.
--
I.N. Galidakis |
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| Don Klipstein... |
| Posted: Fri Jun 20, 2008 6:23 pm |
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Guest
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In article <1214004186.167512 at (no spam) athprx03>, I.N. Galidakis wrote:
Quote: Continuing a discussion which popped up a while ago, about insects and light:
Two days ago I was required to do several tests to determine whether several
diamonds were fake or not. One of the tests was a UV test.
After I finished the other tests, I fired up my PHILIPS HPW 125W blacklight
mercury vapor. The test was concluded after I placed the diamonds close
to the HPW arc and saw whether they fluoresced bright blue.
Half an hour after I finished, my eye's corner caught the movement of a huge
roach, around 2 inches long, running in the living room.
<And another story of mercury lamps and roaches>
Quote: These beasts appear able to see the spectrum from 365nm to 400nm and they
will gladly "zoom in" whenever they see an appropriate source. I am aware
that insects can see in the UV some, but I wonder what the purpose for
this specialized roach vision is, because large roaches here dwell in
sewers, where there is absolutely no need for such light.
I doubt this is specific to these roaches. Over the years, I have
gained an impression that insects in general can see much of the UVA
range.
As for roaches specifically being attracted by UV - I don't know the
explanation. I have tried various lamps in a homebrew bugzapper, and I
found most insects attracted by a broader band including blue-green, blue
and UV - but especially blue. Maybe some insects like UV - light from
clear blue sky is often rich in that, so maybe insects that come out at
dusk might like UV or anything that looks like sunless blue sky.
My experience is that the American cockroach (large, adults sometimes
fly especially in very warm weather) often comes out at night to scavenge
for food. Possibly it thinks that UV lamps or blue-fluorescing curtains
are the way out from a hiding area to a just-dusk-befallen scavenging
area?
- Don Klipstein (don at (no spam) misty.com) |
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