biologe

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Tag: Eudicella colmanti

Eudicella colmanti – Mating behavior of a colorful beetle

Rose chafers represent a group of colorful beetles, which taxonomically belong to the Scarabaeidae and thus are relatives of famous beetles such as Scarabaeus sacer, well known for rolling dung into balls and for being an important symbol for creation and the rising sun in the ancient Egyptian world. Even the stag beetles are more distant relatives of rose chafers.

 

Colorful and active during daytime

 

Unlike some related beetle clades, rose chafers are usually active during the day. This is also indicated by their very colorful bodies. Colors in insects can have different functions, but they usually all are optical signals, which require a visibility in the sun light. Greenish colors are common in rose chafer species and might have optical inner specific signal functions, but also might support an optical camouflage. This would also make sense in the preferred habitats of the adult beetles, which usually feed on softer parts of blossoms and on their pollen. But they also feed on fruits, whereby mostly liquids are incorporated as the chewing mouthparts are not very well developed.

 

Tropical rose chafer Eudicella colmanti during its copulation behavior, 4K videography, copyrights Stefan F. Wirth.

 

Tropical rose chafers from African countries

 

About 3000 species of rose chafers are known, of which most inhabit the tropical zones. The about 20 species of the genus Eudicella are more or less restricted to the African continent.

Eudicella colmanti is native to Gabun, Kamerun and Kongo, thus a species with a main distribution in Central Africa. But E. colmanti is like other species of this genus worldwide often kept in terraria, although species like E. smithi are more common inhabitants of this kind of artificial habitats. They all can be more or less easily reared.

 

Specific flying mode and copulation behavior

 

This is why I was able to study behavioral characters in detail. And rose chafers indeed show interesting behaviors. They for example perform a unique way of flying. It is a specific character of rose chafers (a so called apomorphy) that they fly with closed fore wings, which cannot be opened as in other beetles.

I documented in my video the mating behavior of a beetle couple. Interestingly this was not too difficult, although both genders can, when separated from each other, react to disturbances with a high agility.

 

Almost permanent copulation activities

 

But in the copulatory position, they accepted to be removed from their terrarium to the filming set and even stayed in position, when they were enlighted from different positions with very bright light beams. Please note the the female, which I observed regularly actively searching for a position underneath the male (behavior not clearly visible in my footage). But it also conspicuously never stopped feeding (on an apple) during the copulatory process (very well visible in my footage), obviously to obtain enough nutrients for the production of eggs. A copulation in my couple is not a unique event, but is repeated regularly and can take hours.

 

Phoretic mites

 

Both genders carried bigger numbers of mites. These were phoretic deutonymphs of the taxon Astigmata (Acariformes, Acaridae). As never determined the mite species, as it was not clear, whether it represented a natural associate of these tropical beetles, or whether it was a species native to Germany, which for example was carried into the terrarium via Drosophila flies.

Copyrights Stefan F. Wirth, Berlin March 2017/ February 2019

A scarab beetle’s larva and pupa: habitats for mites and other organisms

The micro-world is complex. Its habitats intertwine themselves, some even are unusual, because they are formed by single animal individuals. An example is a holometabolic insect, here the tropical rose chafer Eudicella colmanti. The larvae of my specimens are covered with deutonymphs of an astigmatid mite (Acaridae, eventually Acarus sp.).

This makes the beetle larva to a habitat for these mites, although the mites in this case don’t feed or reproduce there. They instead are „only“ passengers on their transportation to a new „real“ habitat, where they become adult, feed and reproduce. This strategy to be carried by other organisms from one living place to another is called phoresy.

The situation in my terrarium might be artificial in the sense that mites are putatively not of tropical origin as the beetles (reared in Germany) and thus do not originally „belong“ to the beetle species. The mites might have reached into the terrarium via fruit flies or similar native organisms or via the terraria of the online shop, where they were bought. But the mite deutonymphs show a distinct affinity for adult beetles and their larvae nevertheless, which they attached in great numbers (not the pupa). The microscopic footage of the mite deutonymphs contains activities of their genital openings, located close to the sucker plates on their undersides.

They occasionally open and close and discharge secretions or water. This might be due to osmoregulation and/or in order to prove the adjacent sucking structure with moisture for a more stable hold.

The larva after some months built its pupa chamber, consisting of soil particles and larva secretions. Tese pupa chambers offer on their outer sides obviously enough nutrients for collembolans, which appeared there in greater numbers, especially on an older chambers with its pupa waiting to hatch. Mites of the Gamasida and tiny annelids could also be observed there. The video consists of macro fotage and microscopic footage, all recorded in 4K and rendered in an uncompressed quality.

 

Berlin, December 2017/November 2018, copyrights Stefan F. Wirth