Atyphella atra

Our research centre is now into the seventh year of an ongoing study of our local fireflies.
As we appear to have two distinct breeding colonies of fireflies in our research area, from 2009 onward a new study will commence with the observations being done in the new area which is more accessible by vehicle.

We have four species of firefly in our research area. The most numerous species in the Purlingbrook area of Springbrook Queensland has been identified by Dr. David Britton, Entomology Collection Manager at the Australian Museum in Sydney, as Atyphella atra.
Ballantyne and Lambkin’s key –  Atyphella atra Lea (Lampyridae: Luciolinae).  The species appears to be limited to patches of suitable montane rainforest in SE Qld-far northern NSW,  including Lamington Plateau (incl. Wiangaree), D’Aguilar Ranges, and Conondale Ranges.

Our fireflies are commonly sighted in the in the late spring ( Nov-Dec ), usually in wind protected areas of rainforest with high rainfall.
The duration of their adult lifespan appears short. Ongoing observations of the firefly species found on Springbrook would suggest a lifespan of 4 nights.
Mature specimens retained alive in a moist ventilated flask containing moist forest litter survived for this duration.
Flying specimens caught, observed and released measure average 8mm (all males) in overall body length with the head extended outside the visor shield.
The female specimens found have an overall body length of  6mm.

 

Male fireflies use a flash pattern to attract the attention of females on the ground and use their very large eyes that are shielded from above by a visor when in flight, to detect responsive signals from receptive females.

Female fireflies have only a single abdominal segment in their photic organ underside. Their translucent bodies are used to project a flash pattern upward through their wing shields.

Males have 2 large abdominal photic organ segments.

 

Observation area #1   2003-2008:
The original isolated observation area in the picture below was selected for the first study.
It contains approximately 2 Hectares of forest, a small clearing of approximately 1100sq.metres, a 4 metre high rock wall and a spring-fed swampy creek.
This observation area is at an elevation of 714 metres, surrounded by well established forest for a radius of at least 1 kilometre, and is relatively protected from low wind due to the height of the forest canopy.

The observation area chosen does not include numerous sightings of fireflies in other areas of surrounding forest, it has been chosen because of the known past history as a reliable breeding ground for fireflies.
2005 note:
The clearing, surrounding forest and observation area were the subject of a large weed eradication program in 2004/2005. Lantana had overgrown the original cleared area over the past 40 years. The bulk of the lantana was pulled in mid-winter 2004 with a tractor and cable, and the regrowth and inaccessible areas spot-sprayed with non-residual herbicide.
The success of this action is remarkably evident with larger than ever numbers of fireflies being visible.

hv7.jpg (49450 bytes)OBS_MAP.GIF (15992 bytes)

Observation area #2   2009
orest area at an elevation of 714 metres, on a forested ridgetop in our research area.
This new forested ridge top observation area has been chosen because of the different terrain and more importantly the ease of access for study purposes (gentle sloping ridge top ground without having to negotiate the creek, gullies and rocky outcrops at night in the old #1 observation area.) The only clearing in this regrowth forested area with a canopy height of between 10 to 20 metres is a leaf-littered 4wd track used for access. The forest floor has a low open fern and shrub coverage and the main species are rainforest trees with tall wattles to 15 metres plus a scattering of 25 metre high eucalypts as the upper story canopy. There are no creeks in this area so the area is dependant on rainfall.

 

observation_area2_sm.jpg (50398 bytes)

Click the image for larger view

 

Observations of the random and rather erratic flight pattern of a single firefly in still conditions suggest that it can easily and thoroughly cover around 1100 sq.m. of area in one hour flying at a height of between 3 to 5 metres above the ground. Males occasionally decend to ground level to rest on low ground cover foliage, or to check out possible female sightings. Male fireflies are not strong fliers and can be easily caught by hand whilst in flight.
Male fireflies are also attracted to a small flash of light in the red/orange spectrum.
Strong windy conditions, rain and bright moonlight cause fireflies to abandon their quest for a mate as they appear to be unable to fly in strong wind, and their light producing capability and vision appears to be  affected by bright moonlight. When a full moon rises the aerial activity is noticeably less in intensity.
Fireflies are noticeable in the forest areas at Springbrook 0.5 to 1.0 hour after sunset, usually in large numbers in late November to early December.
The duration of the flashing flight display of mass emergences each night is brief, usually around 30-45 minutes. There are exceptions to the normal with occasional individual males persisting for longer periods, and it is usually these ‘late flashers’ that find a female.
The female on the ground emits light through it’s translucent wing-shields making it easier for a male in flight to distinguish between the sexes.  Male fireflies have opaque wing shields, brown/black in colour.

Note: Scrambling over fallen logs in the rainforest after dark while tracking low flying male fireflies really adds a new dimension to night research. A pair of shin pads has been added to my kit.

Rather than adding notes, a summary of observations to date has been tabled below.

The observation time of 19:30hrs was chosen as the earliest optimal time for November and early December.
The method of counting fireflies in order to retain consistency has been to count  4 x 90° “blocks” in multiples ( 5 to 10 fireflies at a time depending on the size of the display ) from left to right, then from right to left and averaging the two at the same time in the same spot each night. The numbers shown do not indicate all fireflies in the surrounding area, only those at the sighting point.

 

These links will open a new page. Simply close each page to return here.

Nocturnal Field Observations

2003 2011
2004 
2005 
2006
2007
2008
2009
2010
Comparison of firefly emergences from 2003 to the present.
The search for the larvae of the firefly
External notes by interested firefly observers

 


Overall observations suggest that:

1. Energy
The chemical elements required to provide the energy expended by fireflies in light emission is accumulated during the larval stage.
2. Nutrition
The species of firefly being observed here does not feed in the adult stage. It appears to have no visible mouth parts therefore it would have only a limited supply of energy and consequently a short life span (4 nights).
It uses only the existing fuel in it’s body and expends it all in it’s brief four night lifespan session looking for a mate. The tables above are intended to portray an overall observation of fireflies numbers in an isolated area and the conditions that contribute toward optimal breeding periods.
3. Size
The body length of Atyphella atra with head extended outside the visor shield of captured and released male fireflies averages 8.0mm.  It appears also that we have two closely related but different species in the same area. The same phenomenon has been observed recently in the Natural Bridge area. (see pics at the bottom of this page).
4.  Predators
Spider webs contribute significantly toward the reduction of the population as a high proportion of male fireflies meet their demise in webs while flying at low level at night.
5.  Vision capability
Observations of the sight capability of male fireflies in large numbers in a given area show that the greater the numbers flashing in an area, the less likely they are to see a female flashing response from the ground.
I have stood beside a female firefly recently in a period of intense male firefly signalling and observed none finding the female who was responding quite brightly.
When the aerial barrage had declined, one lone male detected the female and descended to the target.
This suggests that even though the male has extraordinarily large eyes, they may be ‘night-blinded’, ‘distracted’ or perhaps forced to be more competitive by ‘out-flashing’ the other male fireflies in the quest for a mate.
6. Duration of aerial flashing display
The duration of the flashing flight display of mass emergences each night is brief, usually around 30-45 minutes. There are exceptions to the normal with occasional individual males persisting for longer periods, and it is usually these ‘late flashers’ that find the females.
7. Larval life span
This has yet to be determined. However observations suggest the life span in the larval stage may be around 12 months.

8. Disproportional representation of the sexes
The ratio of males to females seems to be around 100:1. Females are extremely difficult to find.
The ratio of males outnumbering females at 100:1 has been verified in observations over a 6 year period.
This is the outstanding unanswered question resulting from the observations.

note:   Why are there so few females?  ………..   more work needs to be done on this question, although I would suggest that from observations,
‘the male who flashes longest or last‘,  usually gets the female, and this may simply be natures way of selecting the strongest males for breeding.

Biochemistry of light emission:

Fireflies produce light via a biochemical reaction consisting of :
Luciferin (a substrate) combined with Luciferase (an enzyme), ATP (adenosine triphosphate {the energy 
molecule}).
When these components interact in the presence of oxygen, photon emission (light) is produced.
However by comparison, the method of light production by the firefly although involving the same chemical componentry is quite different to that of the glow worm and ranges through a different colour spectrum.
The colour of the light produced seems to the eye to range from red to orange while building up a charge, through to pale green to yellow on ignition.
The firefly is able to generate a distinct surge of flashing light probably by controlling the oxygen supply to the photic organ for use in the chemical reaction. Unlike glow worms that produce continual light emission, the firefly has the ability to “load” small quantities of chemicals to react with oxygen with a quick flash of light, with each small charge being quickly expended. They are able to repeat the process in rapid succession with the light emission being likened to the flick of a flint ignited cigarette lighter.
The production of light by the firefly is very efficient, with very little heat being given off as wasted energy.

Researchers from Harvard and Tufts universities discovered that fireflies use the same gas that regulates blood pressure and heart contractions in humans.
The gas – nitric oxide – once disdained as a mere air pollutant, controls delivery of oxygen to specialized light cells that use the oxygen to fuel chemical luminescence in the fireflies.
Fireflies rapidly flash on and off with the coming and going of the gas, generating signals that identify the species and sex of the flashers.

Trả lời

Email của bạn sẽ không được hiển thị công khai. Các trường bắt buộc được đánh dấu *