Green (1909a) indicates that adult females are at first pale bright green, dorsum powdered with white mealy secretion; afterwards greenish ochreous. Living adults flat, emerald-green in color, with some black or very dark brown minute dots set in irregular radiating rows near the margin of the body; old adults flattish, color evenly dark brown. According to color photographs of Wong et al. (1999) immatures are light green to cream (probably early 2nd instar males before forming male sac); male sac white, with midline projections.
Megapulvinaria maxima is similar to M. maskelli by having denticle located on widest part of claw; marginal setae of 2 kinds; tubular ducts scattered over venter; apical setae enlarged; third antennal segment unusually large. Megapulvinaria maxima differs by having more than 3 stigmatic setae (3 in M. maskelli); no periopercular (present in M. maskelli).
U.S. quarantine notes
This species was intercepted 2 times at U. S. ports-of-entry between 1995 and 2012, originating from Indonesia, and Thailand. Previous interception was on unknown host leaf from Indonesia. Two older interception records are from Thailand on Mangifera indica and The Philippines on Bougainvillea. ScaleNet includes hosts in 14 plant families from the Australasian (Federated States of Micronesia; Papua New Guinea) and Oriental (various countries) zoogeographic regions. No other species of Megapulvinaria have been taken in U. S. quarantine.