Scotorythra ortharcha (Geometridae)



Scotorythra ortharcha caterpillar

Side pattern larval form

Scotorythra ortharcha larva

Diamondback larval form








These are the two most common forms. Occasionally the caterpillars are solid green.


Scotorythra ortharcha female

Adult female

Scotorythra ortharcha male

Adult male








The female forewing usually has the broad white bands, while males have the same markings over uniform dark grey.

This species was supposed to be combined with S. oxyphractis by Mandy Heddle, who reworked the taxonomy of the genus for her dissertation at UC Berkeley. I have arbitrarily chosen to call my specimens “ortharcha” which may not be the final name.


Host plant recorded from the Alaka`i Swamp:

Caterpillars feed entirely on the young leaves which are thin and reddish in color. Old leaves of Smilax are very thick and tough. S. ortharcha was rare in 1999 when there were few new Smilax leaves available, but more common in 2000, when the Smilax was leafing out furiously.


Development time in the laboratory at 20°C:

  • Larva: 4 weeks
  • Pupa: 3 weeks

S. ortharcha and S. arboricolans are the fastest developing of the Scotorythra, the former perhaps because it can only eat the young foliage.


Larval parasitoids recorded from the Alaka`i Swamp:


It seems probable that Cotesia marginiventris also attacks this species, as it does other Scotorythra. My sample size for this species was lower than for others.