By: Dr David Britton, Michael Hugill, Category: Science, Date: 05 Sep 2012
Somewhat notorious due to their sinister appearance, it's a mystery why death's-head hawkmoths do not occur in Australia. Entomologist Dr Dave Britton discusses the specimens he found during the Museum's terrestrial expedition to Timor-Leste.
Why is the Australian Museum in Timor-Leste? To assist with conservation planning and more.
One of the principal ways of collecting moths in the field is to use light. The best method is to use a very bright lamp that emits wavelengths of light in the ultraviolet end of the spectrum that are highly attractive to these insects.
This light is suspended in front of a white sheet, and moths that are attracted usually end up sitting on the sheet where they can be held in jars or vials. These lights run on mains voltage, so we usually have to carry a generator to collecting locations, which can limit your options for collecting in remote and inaccessible areas.
We picked particularly dismal conditions to go collecting one night. Road conditions in East Timor are extremely poor, with bits of road missing, steep drops, mud, giant potholes and traffic which often seems to be oblivious of these risks. On top of this, a heavy mist had descended from the mountain tops, so the entire 15km drive from our accommodation to the collecting site was shrouded in a thick fog that limited visibility to 30m or so up the road.
We crawled up the hills until we got to where we thought our preordained collecting spot was situated. We had chosen this spot at the base of Mt Kablaki because it had some remnant vegetation clinging around large limestone boulders that had fallen from the slopes above.
Despite the average conditions there was quite a bit of moth activity. Rain and warm wet conditions often stimulate moth flight, and the absence of competing moonlight also seems to increase flight activity.
We had been collecting for a couple of hours, our jars were getting full of specimens and some of the field workers were starting to feel the cold when a particularly large moth bounced off the sheet and onto the ground in front of me. It was very battered, with most of its scales missing and with frayed wing edges, so rather than getting a jar I picked it up with my hands and got an unexpected surprise.
The moth vibrated its wings violently whilst arching up the abdomen and making a sound that was like a panicked mouse. My first reaction was to drop the moth like it was a hot coal. As a defensive mechanism against naive predators, this worked very well on me. I picked it up again, then realised what sort of moth it was.
It was a death's-head hawkmoth Acherontia lachesis lachesis (Family Sphingidae).
There are three species in the genus Acherontia, all with the common name death's-head hawkmoth, the origin of which is obvious once you have seen the skull pattern on the thorax of a specimen.
Death's-head hawkmoths have some notoriety due to this sinister appearance, and this has been exploited in recent years, such as in promotional material for the movie, 'Silence of the Lambs', where the serial killer character left pupae of the hawkmoth in the mouths of his victims.
There are many older superstitions associated with these insects; In Europe the appearance of one of these moths at candle-light was considered to be an omen of death, whilst in France the 'dust' (scales) from its wings was thought to cause blindness. Despite this dark reputation the adult moths are completely harmless to humans.
They are large, very heavy-bodied insects, with a body length of almost 60mm. The caterpillars feed on a range of plants including sweet potato and tobacco, and could certainly be a pest of agriculture in some areas. The adults are also known to steal honey from bee hives; the European species A. atropos does this without being stung by mimicking the scent of honey bees.
It is a mystery why these moths do not occur in Australia, as the adults are strong fliers, and suitable larval food plants are common. We collected a number of good quality specimens of this moth from Timor Leste for the Australian Museum collections.