August 2010. Does anyone have a clear and obvious way to distinguish between Brontispa, Plesisp and Promecotheca? A question asked by Papua New Guinea.

Morphological features in different species may be variable in key characters, but the two species which are common in PNG are Brontispa longissima and Promecotheca papuana. Detailed descriptions of both the mature and immature stages are provided in Kumar (2001). However, the two species can easily be set apart in the field by their size, colouration on the elytra and the feeding habits.

B. longissima are narrow and enlongate (about 2 mm wide) with yellow brown colouring on the anterior and yellowish red to black on the rest of the elytra. Adults and larvae mainly live and concentrate their feeding on young unopen fronds.

P. papuana is wider (4-5 mm) with the posterior region blue to dark purple with the rest of the region of the elytra orange to yellow in colour. Larvae mainly mine sprouted leaves and adults spend most of their time during the day on the underside of sprouted leaves.

Full reference of Kumar (2001):

Kumar R (2001) Insect pests of agriculture in Papua New Guinea. Part 1. Principles and practice – pests of tree crops and stored products. UPNG Printery, Waigani.