Eusthenes brinae Yang, 1935

Eusthenes brinae male
Eusthenes brinae female
Specimens data: Cameron Highlands, Malaysia, nov. 2002 (©PMPF)

comments: the color of some Tessaratomidae and particularly Eusthenes seems to have physical origin. In the wild Eusthenes sp. have resplendant metallic greenish colors, as can be seen here under on the picture made by Paul Aston from Hong Kong but in the collection they are dull dark castaneous (purplish castaneous in the case of E. brinae). The specimens here above have just been humidified to be arranged for photography, and have partly regained their metallic tinge. It is possible to increase a little more this tinge on collection specimens as one can see hereunder on the picture of the same male specimen, after its back has been immerged in water with alcohol and wetting product for half an hour. This leads to the hypothesis that the color of Tessaratomidae is in relation with the thickness of a transparent external layer of cuticle which is reduce to almost nothing (at least less than the wawelength of visible light) when dry; This would explain why, when humidified, the specimens colour go from purplish castaneous to purple, blue green and green.

E. brinae in vivo
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left, after immersion in water with moistening agent, right after normal moistening for preparation

Yang We-I 1935
Blöte H. C. 1945

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