While observing the male E argiphontes (see photo) we noticed an obvious proboscis being actively extended. The gold-coloured proboscis was clearly composed of two fused, lateral tubes as in other Lepidoptera, and was coiled into the head when not being retracted. The moth was observed to be capable of drinking water using the proboscis suggesting that this structure is functional at least to drink water. How this behaviour integrates into the biology and life cycle of Eudaemonia species is unclear at this time - perhaps it is an adaptation that allows a comparatively lighter body as opposed to needing to store all water within retained body fluids necessitating a heavier body? This could be particularly relevant in the female moths who would be expected to retain a full compliment of ova at eclosion as is seen in other Saturniidae.
Why is this special? Most Saturniidae do NOT have functioning mouthparts or lack mouthparts entirely. There have been reports of certain Saturniidae species including Epiphora and Bunaea having vestigial mouthparts and accumulating around puddles of water, possibly to drink. It is clear that Eudaemonia have functional probosci - this must be followed up by a careful review of the other members of the genus as well as related genera.
Note added: over the course of 2019 we observed that female Eudaemonia troglophylla died quickly overnight in captivity unless they were housed in a cage with available surface water. By spraying the sides of the cages liberally with water every few hours, female moths were kept alive for between 3 to 5 days. Female moths did not freely oviposit on cage sides but liberally oviposited on stems of Albizia when these were provided in the cages. Ova were oviposited in what appeared to be disorganised masses on stems with what appeared to be abdominal scales distributed liberally on the outside of the egg masses. Ova hatched within 6 days and quickly died without feeding. We suspect, again, that water is an intimate and necessary part of the biology of these moths and that newly hatched and extremely small first instar larvae need to drink water before feeding. This will be explored in 2020.
Do they serve a function?
The answer is a resounding Yes! The male E argiphontes in the photograph above may give a clue......... If you look closely you will see that its right hindwing tail-tip is missing.....perhaps due to a bat strike. A recently published study by Juliette Rubin and co-workers at the University of Florida concluded that hindwing tail-length correlated strongly with the ability of specific Saturniidae species to avoid successful strikes by bats on the wing. When they progressively shortened the tail length in the Luna moth or American moon moth, Actias luna, the successful strike percentage by bats went up substantially. It seems that movement of the tail-tip during flight creates an active turbulent space in the air that is fools the bats echolocation sonar such that it strikes at the tail-tip, missing the vital, softer body.
So it seems the longer the tail, the better the survivability. It follows that the further away the tail-tip is from the body of the moth, the more likely it is that the moth will survive. It also follows that the longer tails would be found more often in male Saturniidae as compared to females, based upon a probability function associated with amount of active flight time of the two respective sexes.
But when does a tail get so long that it causes manoeuvrability issues and what shapes do the tails take in flight? If the distance from the body of the moth needs to be maximised one would expect that the tail tips are held at the greatest distance possible from the body. We will be attempting to understand this during our trip to Cameroon from Feb 9-16, 2019 when we intend to trap and film adults (males and females) of the three Eudaemonia species. If we are successful we will be posting images of these moths in flight as well as short movies. By closely studying the images we may learn more about the way these incredible insects survive.
Did you also know......only one of these species has a described life cycle.......and even that has not been published to date. We will attempt to describe life cycles for these and many other incredible insects as well as discover and describe new ecologies, biologies and survival strategies as Cameroon Ark works within its mission to discover, educate, conserve and provide.
We hope that this will be the first of many blogs that will highlight just a small fraction of Congo Basin National Forest. Watch this space for updates!
Andrew
Juliette J. Rubin, Chris A. Hamilton, Chris J. W. McClure, Brad A. Chadwell, Akito Y. Kawahara, Jesse R. Barber. The evolution of anti-bat sensory illusions in moths. Science Advances , 2018; 4 (7): eaar7428 DOI: 10.1126/sciadv.aar7428