Dung Chafers
on 2nd June 2012
found in dung midden: http://ispot.org.za/node/175859
Comments
WoW!
WoW!
OK, I will duplicate them. Although I must confess it is mostly to get you to tell us how on earth you think that this is two species (side by side in the same midden and looking -even with your account so far - identical to mine eye).
PS: I almost discarded the broken one: only included it because I thought it might show some other angle or feature. Never occurred to me that it might be a different sex, let alone a species.
link
Added here, with 2 additional photos (the original midden - see link above, and the beetles in situ in midden) : http://ispot.org.za/node/176728
Title changed from Dung Beetles to Dung Chafers.
Reasoning and motivation
Rhinocoeta armata is the aberrant fruit chafer in Photo 1: upright specimen; Photo 2: top specimen; Photos 3 & 4: intact specimen. Compare this with the notes for the other specimens in these photos, being Rhinocoeta sanguinipes, HERE: http://ispot.org.za/node/176728#comment-71471.
It may be necessary to zoom right in and look at more than one photograph to see these species-specific characteristics:
1. This species is larger and more robust than the other.
2. This species has the body and appendages all black, with no brick-red colouring.
3. The punctures on the pronotum are irregular, not round.
4. The punctures on the scutellum are robust and strongly elongate.
5. The mesosternal lobe of the mesometasternal process is more dilated than in the other species.
6. The tubercle on the anterior margin of the pronotum is large but low, and never absent; the pronotum is evenly rounded up to the tubercle, never depressed behind or beside it.
7. The elytra are coarsely sculptured, but finely textured between the costae, without discernible crescent-shaped punctures.
8. The third and fifth elytral costae are fairly distinct and complete, meeting on the apical umbone.
9. The shapes and configurations of the spines and spurs at the apex of the hind tibiae are strikingly different: carefully look at these structures in both photos 1 & 2.
Additional distinguishing characteristics are not visible on these photos. Please note that the characterisation above does in part not entirely exclude the other four Rhinocoeta sensu stricto species, of which we do not have observations yet.
-- Beetledude
Facinating - thanks!
Facinating - thanks!
Is this one of the species that some ecology is known from?
I still am incredulous that two species of a rare species are in the same midden. Any chance that the one species is the opposite sex of the other ???
Alternatively, what allows two such similar species to co-exist? In plants it would be almost inconceivable for two such similar species to cohabit (and I do not refer to the flowers, but to habit, leaf shape and size, etc. We have to exclude sex organs as they would have to differ in some feature - naturally, although this need not be morphological (e.g. season, time of day, colour, etc.)).
PS
Sorry, I neglected to say that you did find almost a dozen differences! But if we had to define plant species on this level of difference we would have thousands of species of Erica!
Prof Schelpe always used to say a good species is what a good taxonomist says it is! He never admitted though that although we cannot have bad species there seem to have been quite a few bad taxonomists, at least according to other taxonomists.
But I guess if one has to count bristles on a fruit flies shoulder to ID it, then it is more a case of most plants having visible differences, whereas for insects one has to rely far more on finer differences, not always readily visible to an unaided eye. Especially when we are spoiled by Butterflies, larger Scarabs and other insects where species can readily be identified by sight at a distance.
Reply 1 of 2
On New Year's Day tony rebelo wrote:
>>> But if we had to define plant species on this level of difference we would have thousands of species of Erica!
RESPONSE:
And if we had to define beetle species *only* on this "level of difference", we would similarly have thousands more species of chafer beetle::
The two sides of this coin complement each other:
*** The majority of the characters of which I listed the states above, have been evaluated broadly over the Cetoniinae to be characters that are reliable to distinguish species across this subfamily, and are characters that are often (but not exclusively!) used in contemporary chafer taxonomy. In other words, and for more reasons, they are "good characters". The first one in my list, above, is not an example of a broadly applicable "good character", but it is "good enough" to distinguish between the two species of interest here.
Moreover, the characters that I used in this illustration should be considered in concert, all together, since a selection of only a single among them, or of only a few, will not "make" a good species. Not for the exercise of comparing only two species, as here, but for the enterprise of thorough taxonomy.
*** The species of Cetoniinae are not defined only by characters with "this level of difference", thank Lemonade. ((This is so in properly executed work; at your peril see the rant below)). A suite of "solid" characters are available for the limitation of "proper" (sub)species. Yes, your guess is right, prime among the "solid" characters are the infinitely complex male genitalia so popular among entomologists, who in common ascribe to the theory that (male) genitalic differences are indicative of species boundaries. That is because of the pervasive acceptance (albeit often denied!) of a Mayrian species concept, which hinges on reproductive isolation, seen together with the lock-&-key theory. This theory serves us well, despite more recent reports that it breaks down in some spider families.
I have the SA Fruit Chafer Bible (Holm & Marais 1992 ... it is getting old) open to the left of me. Even in gross morphology, the male organs of Rhinocoeta armata and Rhinocoeta sanguinipes are very different. To a trained eye, that is.
.
RANT:
Cetoniinae (fruit / flower chafers) are charismatic, beautiful, popular, very collectible, very saleable, and ... superficially very variable. They are one of the prime targets, among beetles, for one of the main activities of naive taxonomists (both professional and amateur): the never-ending description of dubious "species" and "subspecies", among the Cetoniinae based on variable characters of little or no systematic value.
Doubtful new species are a real problem in various taxa, as you certainly know. One feels inclined to just ignore any "contribution" by certain authors, but scholarship (and the Codes) oblige the professional or serious taxonomist to take note of every new name that is technically valid, and evaluate its worth. This is a great waste of time in taxonomic practice. Whereas a large contingent of non-professional taxonomists churns out some top-notch systematics, an irritating complement of naive (or deceiptful!) (or moleculoid!!) taxonomists and "taxonomists" contribute to the Taxonomic Impediment.
I get down from my soap box now.
-- Beetledude
So to go back to Schelpe and
So to go back to Schelpe and competent taxaonomists "knowing" what a species is.
Most species on earth have a few million years under their belt. Getting to grips with the taxonomy is primarily one of understanding which features are useful and which are not (and which are downright misleading).
So I guess my quip was uncalled for. Except that I am convinced that if botanical taxonomists were to be as pernickety and thorough as many entomologists, we could probably have a working key for each local population of our more common species (I can only speak for the Proteaceae and Ericaceae that I know best, but I am willing to bet it applies to species in many Fynbos plant families).
Reply 2 of 2
Forthcoming. First read the other one.
-- Beetledude
Truly an unusual observation
The beetles in this fantastic observation are not dung beetles, but enigmatic "fruit" chafers of the subfamily Cetoniinae:: genus Rhinocoeta.
Rhinocoeta sensu stricto consists of six known species (one recently detected and still undescribed), restricted to arid or semi-arid, sandy habitats of the western and southern Cape, Karoo, Namaqualand and Kalahari. These beetles are seldom encountered and are rare in collections.
The genus has variously been called "a relict lineage"; "primitive"; or "most primitive", but in actual fact its phylogenetic placement is completely unresolved and presently contested.
The biology and ecology of Rhinocoeta species are almost completely unknown. Only for two of the five named species have adults of both sexes ever been found. About one of the described species nothing is known except that it occurs in southern Africa. And despite substantial searching effort, another described species has not been recollected since 1879, and was considered to be "probably extint" by Holm & Marais ('Fruit Chafer Bible' 1992: 170).
The larva of one of the species is known and has been formally described. Unusual among the Cetoniinae, adults of Rhinocoeta have never been observed to feed on flowers or fruits, but are instead generally collected under dung pads of cattle or in dung middens of a variety of indigenous antelope [like this observation]. It has been claimed that the adults are nocturnal fliers, which would also be unique among the Cetoniini.
Doubly remarkable is the fact that there are two different Rhinocoeta species in each of these photographs. Really. (Fortunately(?), they seem to belong to two described species). PLEASE SPLIT THIS OBSERVATION INTO TWO, which in fact means duplicating this observation. Species A is depicted as follows:
Photo 1: The upside down specimen.
Photo 2: The bottom specimen.
Photos 3 & 4: The broken specimen.
Species B is of course the other specimen
Please do not discard either Photo 3 or 4: different details are discernable on each. And then I will (touch wood if you can find some:) return to identify these weird creatures.
-- Beetledude