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A broad observation of these interesting creatures
reveals the following :
Glow worms are the larvae of a large
mosquito-like fly that have a very unusual lifestyle.
||Here we have a photo of male and female flies
mating adjacent to a pupal casing from which the female fly has emerged.
image for full frame shot
Glow worm flies in the Springbrook area are of the
Arachnida, Arakhne ~ spider , (L. Gk.)
( literally a grub that uses a web like a spider to catch it's prey ).
Subgenus flava Harrison 1966: 880.
Type species: Arachnocampa flava
Glow worms elect to inhabit
a wide variety of terrain including shady protected places with high humidity but not
necessarily constantly wet,
and at Springbrook they can be found in:
- the earth walls of roadside cuttings and tracks
- crevices in rock faces
- creek banks
- under protruding rock ledges behind waterfalls
- under rocks on the ground that have a protruding ledge
- and the root masses of large fallen trees.
our Glow Worms .
our glow worms are a subject of ongoing study at the
Springbrook Research Centre, we value them highly and
ask visitors to kindly observe the following when
visiting the glow worm colonies.
Glow Worms being nocturnal are adversely affected by
indiscriminate shining of torches upon them.
They have developing eyes shrouded by a thin layer of
protective skin, however they can see light.
Excessive torch light makes them react as they do to
sunlight by ceasing light production and hiding in
their refuge, usually a crack in the rock wall or
earth bank behind their webs.
Flash cameras can actually kill the Glow Worms.
It's not the first flash , but the subsequent flashes
that damage the Glow Worms eyes and affect
their ability to function.
Glow worms being insects are adversely affected by the
odour of insect repellants, and also some
'overpowering' body perfumes.
smoke contains nicotine which is an insecticide,
consequently smoking is not permitted in our research
||Glow worm web illuminated by the glow worm.
Night photo by Belinda Janke.
click the image for larger view
The use of webs for
In order to survive glow worms build elaborate traps consisting of anywhere between 10 to
50 plus hanging threads of silk studded with sticky droplets of mucus
as a form of glue to catch
small insects such as mosquitoes, midges, fruit-fly, gnats etc. that are attracted by the
light produced by the glow worm.
The pendulous web strands are attached to a lattice-work of silk threads across the
ceiling of their lair. In turn the threads support the suspended mucus
tube in which the
glow worm resides and travels, enabling the glow worm to be attracted to the vibration of
A typical web strand showing the droplets is displayed on the RHS.
The length of the glow worm's web depends on the exposure factor .
If protected from the wind, strands can be as long as 100mm.
Web strands in exposed areas rarely exceed 20mm.
Because the web strands are 'weighted' with drops of 'insect glue' the whole web seems to
be perfectly balanced and individual strands pendulate in unison in light breezes without
tangling. Strong winds however cause the glow worm to spin shorter
webs to avoid tangling.
2005 note: The writer suspects the droplets on the silk webs may
contain a tranquilliser as insects that become snared
don't struggle as they do in a spider web.
A study into insect "glue" was being pursued
in 2005 by the CSIRO.
Unfortunately our sample provided for this study in a sealed glass container dried out in
transit before analysis could be carried out and no solvent
currently available was able to dissolve
makes a glow worm glow ?
A. Glow worms are oxygen intolerant.
So they use a very simple but ancient chemical reaction to burn off
their body waste that results in the oxygen being reduced back into
water which is
then passed as a bi-product of the chemical reaction.
||Glow worm tail
close-up at night.
by Stuart Webber
Click the image for a larger view.
Glow worm waste product=Water
||At last....photographic evidence !!!
This photo by Stuart Webber here at the Springbrook Research Centre
has at last achieved photographic evidence of a process that I have been seeking for many
years, i.e. water being expelled from the glow worm's body as a waste product.
The water produced accumulates in the
mucus tube in which the glow
worm resides until it creates a weak spot into which to drain. The subsequent 'pendulous
bag' bursts and the water falls to the ground. The lesion created by this action in the tube is sealed over by the
excretion of mucus from the glow worm's body.
Click the image for a larger view.
The blue/green glow of the larvae is the result of a reaction between body products and
oxygen in the enlarged tips of the larvae's excretory tubes. The light is the result of a
chemical reaction involving several components:
||( a waste product of the organism containing a
specific molecule that undergoes a chemical charge when affixed by an enzyme. )
||( the enzyme that acts upon luciferin )
||( the energy molecule )
All these combined make an electronically excited product capable of
emitting a blue-green light.
To the average person's sight, up close the light appears more blue than green.
Spectrometer readings show the colour is actually in the green colour spectrum.
Direct moonlight affects viewing of glow worms in
exposed area colonies .
Only the brightest glow worms in exposed colonies are visible on full moon nights.
Immature glow worms cannot generate sufficient bioluminescence to compete with bright
moonlight and whilst they are in fact glowing they appear not to be.
Glow worms have the ability to very quickly shut down the bioluminescent reaction and
cease glowing in the event of a sudden large disturbance of their webs.
The name glow worms is a misnomer as they are larvae, not worms.
Early settlers from the British Isles probably applied the common name 'glow worm' as a
substitute for the English glow worm Lampyris noctiluca, (actually beetle
larvae). As the name 'glow worm' is more aesthetically pleasing than 'glow maggot' or
'glow larvae', this probably accounts for the adoption and retention of the
In colonies that are exposed to outside weather conditions , it is not unusual to observe
a variety of small spiders sharing areas where the glow worm builds it's web sometimes
covering the whole glow worm web area and using the light produced by the glow worm to catch insects. This deprivation of
their food source may be a contributing factor to migration as some do of necessity move
around finding more favourable locations . Overpopulation of glow worms in the initial
hatching areas of necessity causes migration otherwise they tend to eat each other.
Natural erosion of soil areas also causes migration to occur and the patterns of colonies
here in the soft earth-bank colonies are constantly changing. The writer has observed a
free-fall of glow worms from a height of 8 metres due to erosion in a soft earth bank. The
glow worms that were not crushed by the fallen soil survived and re-located.
The life cycle of a glow worm involves four stages: egg, larva, pupa and adult fly.
Eggs are laid in small batches directly onto the walls of the
Depending on the seasonal conditions at the time of egg-laying, the emergence of larvae
from the eggs can take anywhere from three to six weeks to hatch. On emergence the tiny
larvae immediately start glowing from their tails. The head of the
larvae is hard and the body soft. A larvae sheds its skin
(moults) several times throughout its life.
Due to the proximity of eggs laid in each small batch, cannibalism
can occur if there is an absence of small insects to
become food for the larvae.
Observations of egg numbers from a single fly in the underground controlled environment
performed in 1997 revealed that losses due to natural causes and cannibalism accounted for
70 out of an initial laying of 120.
It must be conceded that these losses may not be as high in the natural environment due
to a wide ranging variety of small insects and fungi that are potential food sources for
the larvae being naturally occurring.
Due to the erratic egg-laying paths taken by flies it is not possible to compare the above
losses with those in the wild without creating a false environment that in turn would
defeat the purpose of the exercise.
Newly emerged female fly
adjacent to the pupal casing from which it has just emerged.
click image for full frame shot
documentation by others suggests that the larvae grow over a period of eleven months until
they reach a length of about 25mm .
Note: The writer is not convinced that these publications are
correct as at least two and possibly three breeding cycles per year , depending on
seasonal factors , have been observed in our outside colonies which suggests that the
lifespan is much shorter. This combined with observations of actual cycles of emergence in
our controlled environment suggests, that with ideal conditions, a
full life cycle of five months can be achieved.
To verify this statement,
between 2003 and 2004 observations of hatchings were
recorded on 19-05-2003, 08-10-2003 and 10-02-2004.
Early September (start of Spring) traditionally displays the largest emergence of juvenile glow worms even
though it is usually the driest time of the year.
However the 19-05-2003 and 10-02-2004 emergences coincided with above average rainfall in the
preceding month, suggesting that unseasonal rainfall
produces more insect life that in turn will sustain the
When conditions are favourable pupation takes place wherein the larvae exude large
quantities of mucus around their bodies that dries out and shrinks in size to form the
pupal casing, which is suspended slightly downhill of horizontal.
The pupal stage lasts about 12/16 days. A prominent signal of pupation being a
'shrinking' and shortening of the web-strand lengths due to lack of
Seasonal triggers a probable factor in pupation :
The start of the main pupal cycle on Springbrook varies but seems to occur around the end
of August / September which on average is the driest part of the year.
This phenomenon generally appears to coincide with the forming of the flower buds on the
native orchids on Springbrook , suggesting that a change of season may initiate a
triggering of pupation.
Storms also trigger pupation, and in particular lightning
that appears to visually 'shock' females of breeding age
Not all glow worms pupate at the same time again suggesting that false seasonal triggers
due to variable weather patterns causing variable hatchings of insect life upon which glow
worms depend as their food source may be another factor , and more observation is
Note: An ongoing drought in 2003 caused an early pupation in
May in the area of the external colony that is normally quite moist. The drier areas
The writer voluntarily operates the rainfall station at
Springbrook for the Bureau of Meteorology and the chart below shows the average rainfall
at our glow worm facility.
The female pupa is larger and stouter than the male .
Life span of adult flies:
Approximately two to three weeks later adult flies emerge to re-commence the cycle.
Male flies tend to live longer than females and can live up to four days.
The flies have no mouth parts or means of feeding, their role in the reproduction chain is
to mate and reproduce by laying eggs .
Near fully-developed female flies in their pupal casing have the ability to send a
low-intensity glowing signal to male flies at the time of their impending emergence. As a
consequence of their signalling it is not uncommon to observe male flies adjacent to the
pupal casings of female flies waiting for them to emerge.
The entire life of the glow worm larvae is spent inside a suspended
mucus tube with it's
head facing the escape route into a crevice or safety haven in the rock or earth wall into
which they move at remarkable speed when disturbed.
The mucus tube insulates and prevents the glow worm from desiccation.
At night inside the tube it moves back and forth breaking through the tube to repair it's
web or to feed on trapped insects.
During the day the glow worm hides inside it's safety haven of a crack or hole behind the
web to avoid daylight predators.
Interaction between spiders , other
insects and glow worms :
||One of our local "brown rock-hoppers" or
spiders ( 75mm leg span ) waiting for large insects to be attracted by the glow worm's
Many small and large varieties of spider co-habit
glow worm colonies.
The glow worm's light attracts not only small insects but large ones such as bush
cockroaches and beetles as well that can impact heavily on the unsuspecting glow worm. The
larger spiders, particularly the sentinel and huntsman varieties patrol the walls of the
glow worm colonies without disturbing the glow worms and actually protect the glow worms
from large insect impact by catching the incoming intruders.
So here again we have one of those remarkable symbiotic relationships one finds in nature
wherein the glow worms are attracting the food source for the spiders and the spiders are
providing in return a "protection" service to the glow worms.
It is quite common to observe large huntsman, sentinel, trapdoor and funnel-web spiders
living in harmony with glow worms. Many other varieties of smaller spiders also live in
conjunction with the glow worms.
It is not uncommon to observe small spider webs along side the glow worm web and on
occasion actually spun across the whole glow worm's location.
||Another insect that lives in large numbers in conjunction with glow worms
is a soft-shelled brown cricket .
These crickets are found anywhere glow worms are glowing.
04-05-2002: these crickets
have been observed eating the luminous fungi that grow
they don't attack the glow worms, perhaps they mistake
glow worms' bioluminescence for luminous
fungi for they appear to be totally captivated by the
Some crickets stay for hours staring at the glow worms
as if trying to decide whether or not they are
||These primitive looking thorny crickets with
unusually large feelers are also spotted on occasion patrolling the glow worm colonies at
Click the image for larger view
Extremes of temperature particularly very hot winds in the summer or cold dry strong winds
in the winter period have a dramatic influence on glow worm survival. These extreme hot or
cold winds can cause the demise of large numbers of glow worms in exposed locations.
Strengthening the gene pool
It is fairly obvious that female glow worm flies heavily laden with eggs are not the most
agile of flying insects and tend to lay their eggs close to the area from which they have
emerged from their pupal casings.
The height of the rock wall in our main colony is approximately 10 metres.
On strong warm windy days however the occasional female fly has been observed being
"wind assisted" away from the main colony.
How far they can fly due to terrain
difficulties has yet to be determined.
We have successfully transplanted glow worm larvae from other colonies some 2KM away into
the main colony and watch their development with interest.
||This photo shows the glow
worm actually spinning a web strand and depositing the sticky globlets on the thread.
In external colonies where the web strands rarely exceed 30mm in length, the glow worm has
the extraordinary capacity to extend itself almost to the length of the unmade thread,
starts near the bottom and withdraws upwards spitting the web out including the sticky
drops as it retreats. Webs spun in wind-protected environments can be much longer, and
these longer webs are made by repeating the above procedure
and adding additional lengths
to the original.
The web spinning method described above was captured on video
(Click the image for a larger view )
This photo shows the glow worm lying in wait for
(Click the image for a larger view )
(starting to pupate)
Note the shortening of the web strands.
||Glow worm in final pupal
The web strands due to lack of
maintenance will dry out and
disintegrate within 7/10 days leaving only the pupa.
The above text is published for information of
persons interested in glow worms, and is constantly being updated as we learn more about
these interesting creatures.
The text and photos are made freely available for the use of students doing school
projects provided acknowledgement is made of the source of the material.
Commercial use of any of the above Copyright material without the prior consent of
The Springbrook Glow Worms Research Centre is prohibited.
Australian Biological Resources Study
(NEMATOCERA: Arachnocampa v flava)