This work was part of a long-term study (2001 to 2016) of glow
worms (Lampyris noctiluca) at my nature reserve (The
Secret Garden Nature Reserve) located at Old Bursledon, Hampshire (grid ref
SU486091).
On 3 April 2006 I started to use an array of boards to act as
shelters for the glow worms. I was pleasantly surprised by how quickly, and in
what numbers, glow worms adopted the boards that we laid out for them. Out of
140 put down, 80 were used to pupate under and 46 had two or more pupating
under, while two boards had nine under. (Figures 1, 2 and 3).
Glow-worm
larva inspecting a board. It stayed in this position for five minutes before
going underneath to prepare for pupation.
Figure 2
A cluster of five, all males, all at different stages of pupation. Date 29 May 2007
Figure 3
Female laying her eggs under a board on 29 June 2006. (Approx 75% eggs are laid in the first four days and it takes approx ten days to lay them all: Horne 20062016, unpublished)
From our point of view the boards made it much easier to find glow
worms at every stage in their life cycle: from eggs through to larvae and
pupating to adults, male and female. We also found what we now know to be a
parasitic beetle (approximately the size of a garden ant), and last but not
least the lesser glow worm (Phosphaenus hemipterus). I first discovered this at
9 pm on 14 June 2007 under Board 59a which it was sharing with nine common
glow-worm larvae pupating. At the time this was the only known breeding colony
of P. hemipterus in the
UK.
Pupating glow worm on 28 June
2006 my first photo of the parasitic grub.
In the first case there were four grubs and in the
second case, ten. We believe that they were parasitoids that had killed the
pupae rather than as scavengers feeding on an already dead carcass, because
both pupae had appeared perfectly healthy a short time earlier. Lloyd (1973)
reported two species of parasitic flies (from the families Tachinidae
and Phoridae) in other firefly species, but we do not know of any
records from our glow worms.
The following year, on 29
May 2007, I found similar grubs on a female glow worm. I had recorded the same
glow worm as a larva under the same board four days earlier, but at that stage
had not noticed any sign of the grubs. Over the course of the next two weeks I
found more than 30 glow worm pupae, males and females, carrying grubs of what
appeared to be the same species, the last being recorded on 10 June that
year. Some glow-worm pupae supported over 25 of these grubs, while others just
inches away under the same boards appeared to have escaped totally unscathed.
Within a single glow-worm pupa the grubs varied in size, with some three times
the length of other grubs on pupating glow worms collected 5 June 2007.
Figure
5
My first beetle, seen on 1 July 2007. At that time I did not know what it was. I started to get suspicious on 3 August 2007, but it was not till the next year, on 1 June 2008, that I found out that it was a parasitic beetle.
One of many notes in my diary, on 2 June 2007, refers to a larva under board 59/2 at 18:30. Its weight was 242 mg and it was still alive, and anything over 120 mg is guaranteed to be a female glow worm. It would have probably laid around 140 eggs (Horne 20062016, unpublished). But on 8 June 2007 its larval skin was off the end of its body, and it was now infested with grubs.
On 28 May 2008 I started seeing small adult beetles again. Then on
1 June 2008 in my diary I wrote: Very interesting. I saw four of the grubs
around a pupating glow-worm larva which was still alive when I noticed that one
of the grubs appeared to be biting at the glow-worm larva! This did not
make sense to me, and unfortunately I did not follow this one through, as too
many things were going on. On 4 June 2008 I found four adult A. scapularis beetles
hanging around a large female glow-worm larva. I managed to catch them with the
glow-worm larva and put them into a small tub. Later, at home, I managed to
take some photos of a pair of beetles mating on the side of a glow worm (Figure
6 and Figure 7 close up). The glow worm was still alive, but very sluggish and
at a point of no return into pupation. I managed to take a series of photos
over the next 12 days. I will let the photos do the talking.
Figure 6
Taken 4
June 2008. Mating pair of
beetles on the side of a very sluggish glow worm at the point of no return at
17:40. I was to see this in the wild many times over the next few years.
4 June 2008. Close
up of the beetles
On 5 June 2008 I took them to
the British Natural History Museum to meet
Max Beckley who also confirmed this as a parasitic beetle and said I should do
a report on my findings. Eight
years later I am now doing it!
I did offer to leave the glow worm with the parasitic beetle in my
tub with the Natural History Museum but they declined, saying that they are
very good at preserving things that are dead, but are not very good at keeping
things alive, so why don't you do it. I am so pleased I did this, but it was
one of many things going on at that time.
Figure 9
6 June 2008. This carried on for about 2 hours.
Figure
10
6 June
2008. Testing for any movement?
Figure 11
6 June 2008. The beetle checking for any movement.
Figure 12
6 June
2008
Figure 13
6 June 2008. At
20:59 they appear to be getting quite excited and are now looking underneath
the unfortunate glow worm. Then 43 minutes later in the next picture this
happened.
Figure 14
6 June 2008. I was looking at some of these close-ups, and noticed what looked like
the first grub, then the next photo shows it in a different position. This is
at 21:43, and mating took place on the 4 June 2008 at 17:40, so you can say it
only took two days from mating to a grub. The only thing is there were two
pairs of parasitic beetle in there so I cannot guarantee that it took two days.
Figure 15
6 June 2008. You
can see the different position.
Figure 16
Three days later on 9 June at 21:35 there is a
visible grub, One thing that I cannot get over is how dedicated the parents
are.
Figure
17
9 June. Close up of the above. If the parents are the size of garden ants then the grubs are like a fine
hair.
Figure 18
Two days later from the last picture, on 11 June at 22:48,
look how big they are now quite amazing, I think. Note one beetle keeping an
eye on things.
Figure 19
A day later on 12 June at 15.29.
Figure 20
Same day, at 15:35. Some holes in her back and one adult
beetle in view. Notice that the holes are in the centre of the shields on each
side.
Figure 21
Two days later, on 14 June at 19:32. Nearing the
end now.
Figure 22
14 June, 19:35. The grubs are on the move getting ready to pupate.
Figure 23
On 15 June at 10:05 the last grubs are inside and outside,
with nothing left but the shell.
Figure 24
15 June 2008. This is the last photo of this series
of pictures.
Notes from 2009
On 8 June 2009 I took some photos of a female that was glowing and
had attracted three males. In the photo just two males are showing. When I got
home I looked at the photos and to my surprise there was a parasitic beetle on
her shield. You can see how small this beetle is. It would be very interesting to see if any one else has taken a photo or has seen this. I just wondered
what it was doing. In the series of photos to accompany this, there is what
appears to be a start of a hole in the centre of one of her back shields on the
photos.
Figure 25
8 June
2009. Close up.
Figure 26
8 June at 22:45, showing the parasitic beetle on her head with two
males trying to mate with her.
Figure 27
Next morning, 9 June,
I found the female glow worm near to the spot I saw it displaying last
night. This one was not under one of my boards. Note the start of a hole!
Figure 28
Close up of figure 27.
Figure 29
Now the beetle is at her rear end .
Figure 30
Close up of figure 29. Note that the female glow worm is
mating with a male and the parasitic beetle is looking on or is there more to
this?
Figure 31
The parasitic beetle now on the males head is he next?
________________________________________________________________
You could ask yourself, why has someone not discovered this
before? To my knowledge no one has put boards down, and to try to find this out
in the wild would be like looking for a needle in a haystack. How do the glow
worms find the boards? In May the glow worms that are ready to pupate go on a
walkabout. This iswhen people can see them wandering around in the day time. They
are looking for somewhere suitable to pupate, such as a small hole in a bank, a
crack in the ground or the fibre roots of grass, as well as many more places.
When they come across a board that is about 6 ins by 10 ins or 15 cm by 25
cm the male or female will walk across the board more often. The
boards act as a funnel to guide them in. The downside to this is that the
parasitic beetle probably can do the same much more easily under these boards.
I personally think that this is a natural cycle and one reason why
on average, a female glow worm lays just approx 110 eggs each (Horne
2007/2016, unpublished). It is not a threat to our glow worms and is just
part of life. Glow worms fluctuate year on year through peaks and troughs
and the parasitic beetle keeps them in check.
When there are more parasitic beetles, glow worms numbers may drop, and
when there are fewer parasitic beetles, glow worm numbers may rise.
Over the years, all my reports of this are from my diary and
photos. It starts on about 15 May and finishes by approx 14 June with one exception
on 1 July 2007 when I found a parasitic beetle investigating an adult female
glow worm leaving the remainder to carry on and breeding in peace.
Summary
In conclusion, the above report is just a small part of the information I have about the parasitic beetle. I have included just the main points, and I also think the pictures tell you more of the story for themselves. I believe most of the report is new to science in the UK and possibly in the world.
Finally, I wish to
stress that I am very much an amateur naturalist with no formal training and my
experience and knowledge have been built up through a lifetime of patient
observation and an inquisitive mind.
John Horne, December
2016. Email: horneja@btinternet.com