Body elongate oval; dark red or purple; body unevenly covered by thin layer of white mealy wax allowing body color to be visible, with 2 lateral bare areas on posterior two-thirds of dorsum; ovisac covers most of body; with 1 pair of short to moderately long, slightly curved caudal filaments, occasionally with 1 or 2 other inconspicuous filaments adjacent to caudal pair. Occurring on all arboreal parts of plant.
Balanococcus diminutus is similar to several species of Trionymus by having a small number of cerarii, a small circulus, and multilocular pores and oral-collar tubular ducts on both body surfaces. The New Zealand flax mealybug can be distinguished by having oral-collar tubular ducts with a prominent sclerotized collar.
U.S. quarantine notes
This species was intercepted at U. S. ports-of-entry 8 times between 1995 and 2012, with specimens originating from Italy, New Zealand, Russia, and The United Kingdom and N. Ireland. We also have examined specimens taken in quarantine from New Zealand (Phormium) and The United Kingdom and N. Ireland (Phormium). ScaleNet lists hosts primarily in Agavaceae (New Zealand Flax, Phormium sp.), but there is one record for Scrophulariaceae. It is most commonly intercepted on New Zealand Flax. ScaleNet distribution records for B. diminutus include various locations in the Australasian and Palaearctic zoogeographic regions, and California (The United States of America) in the Nearctic region. One species of Balanococcus other than B. diminutus has been taken in quarantine at U. S. ports-of-entry, B. takahashii McKenzie (South Korea, on Zoysia).