Scale insect as its common name implied is a type of insect that look like a scale. They belong to the superfamily Coccoidea. A week ago, I noticed many ants marching up and down my potted “mini” Ficus variegata (Common Red-stem Fig). The plant was considered mini as it was supposed to be a large tree if it thrived well in the wild. After residing several years in that pot, the plant had already reached its fruiting age and did bear some figs previously.

Those ants in action were the small resident ants (Pheidole parva) in my plant pots. These soil-dwelling ants had adapted very well to the potted habitat for years now. Based on observation on their activeness over time, their population fluctuated based on the quantity of food source available.

I followed their trail to the part of the plant where most of them gathered and appeared to be feeding on something on the twigs. Looking closer at the area, I could see many scale insects of different sizes being tended by the ants. Nothing too surprising since it was a known fact that ants farmed scale insects, and such scale insects had appeared on my plants occasionally. I had always been wondering how the first scale insect got onto the plant to kick-start the population.

In general, scale insects were not active creatures although they had legs under their scale-like body. While the females resembled a scale, the males looked like a tiny fly or wasp. Due to their small body size, identification of the species was rather difficult.

The matured form of the scale insects on the fig plant was black in colour. Nymphs of various size spread across the twigs were either mottled (late instar) or translucent-yellow (early instar). I captured tiny wasp-like insect mingling among the scale insects in one of the pictures taken which I originally thought might be a male form of the scale insect. It was discovered when I was inspecting the photos in my computer. After further checks, it was likely to be a parasitic wasp (might be a Coccophagus species) attracted by the scale insects. Based on what I could find online, the scale insect was identified as Black Scale (Parasaissetia nigra).

Separately in late July, I noticed many Ghost Ant (Tapinoma melanocephalum) gathering on the twigs of a Citrus plant in my pot. This Citrus plant was germinated from mandarin orange seed that was deposited in the pot. The plant was kept as host plant for caterpillars from the Lime Butterfly (Papilio demoleus malayanus).

The scale insect on the Citrus plant was the Yellow Cushion Scale (Icerya seychellarum), a relatively common species. The matured form was white in colour with many long fine hair-like structure. Late instar was yellow and early instar was faint brown in colour.

After taking the pictures, I removed the scale insects together with the affected branches to prevent them from killing the Citrus plant. As for those on the Fig plant, I planned to remove them as well at a later date. Monitoring ant movement had been a good way to detect scale insects on plants.