Post by wollastoni on Apr 8, 2016 20:19:43 GMT
Delias stresemanni is a Delias species described by Lord Walter Rothschild in 1918.
The species is endemic from the mountains of Ceram island in the Moluccas, Indonesia.
Collectors are not so interested in it because its classic form is rather dull for a Delias
Though in 1920, George Talbot described various forms of this species in his Monograph about Delias genus.
This is what Talbot wrote :
D. stresemanni form oenus male / female :
Distinguished by the absence of any band on the underside of the hind wings
Occurs together with other forms. Type in the Hill Museum
D. stresemanni form mediofasciata female :
Hind wing below with a broad yellow or yellowish-white discal band from the costa to the inner margin
Occurs together with other forms. Type in the Hill Museum
D. stresemanni form lutea female
Upperside buff-yellow instead of grey.
Occurs with the other forms at 6,000 feet. Two specimens obtained. Type in the Hill Museum
D. stresemanni form basiflava female
Hind wing below with the proximal area to beyond the cell yellow or yellowish white, some admixture of dark scaling in the basal area. Occurs with the other forms and found at 3,000 and 6,000 feet. Type and three others in the Hill Museum
Unfortunately George Talbot illustrated none of these forms in his Monography. Neither did Leslie Day on the Delias website one hundred years later.
As Talbot indicated the number of specimens found for forms lutea and basiflava, they should be the rarest forms.
Of course this mystery picked the attention of the Delias collector I am. I wanted to see how those forms would look like ! I wanted to see if other forms would exist.
During years, I received a lot of Delias stresemanni, I focused mainly on females as 3 of those 4 forms are described by Talbot as female forms.
I can now picture here most of these forms and complete some of the information written by George Talbot in 1920.
70% of stresemanni I observed were like this. Male are form oenus, female with a bit of yellow suffusion on HW.
15% of females are form oenus, without yellow suffusion :
15% are form mediofasciata, but unlike what Talbot wrote, this form also occurs rarely on male !
Males were said to not vary, truth is they do vary :
I had the luck among all the stresemanni I received to find 2 females of the rare form basiflava. This is a wonderful form !
Here is a part of my stresemanni to give you some direct comparisons between forms :
Oh and as nature is fun, look at the 3rd specimen of the second column... it is a biform ! Classic on the left, form mediofasciata on the right !
I did not found any form lutea and would be interested to see the Type which must be in BMNH if anyone could help on this ! Thanks in advance.
Form lutea is a upperside form which may be only an ab.
I am happy to be able to show these forms to everyone on the ICF.
Now there are still some questions :
- as mediofasciata males have been found, maybe basiflava males also exist !
- there is a clear progression from form oeneus (no yellow) to form basiflava (nearly all yellow), this leaves no space to other forms. I highly doubt another distinct forms would exist.
- is lutea a genetic recurrent form or an aberration
I would like to thank Detani san, Bernard Turlin and Nicolas Grimaldi for their help in my research on Delias stresemanni.
Olivier.
