Melastomes are generally not pest magnets compared to some other houseplant families, but a handful of the usual indoor-growing culprits do show up occasionally, especially on stressed or overwatered plants.
Spider mites
These are the most common complaint, particularly in dry indoor air during winter heating season. Look for fine webbing on the undersides of leaves and a stippled, slightly bleached appearance on the leaf surface. Raising humidity and periodically rinsing foliage under lukewarm water goes a long way toward prevention.
Mealybugs
These show up as small, cottony white clusters, usually tucked into leaf joints or along stems. They're slow-moving and relatively easy to deal with early — dabbing individual clusters with rubbing alcohol on a cotton swab is often enough for a light infestation before it needs anything stronger.
Fungus gnats
These are more of an annoyance than a serious threat to the plant itself, and they're almost always a symptom of soil that's staying too consistently wet. Letting the top inch or two of soil dry out fully between waterings usually resolves the problem without needing any additional treatment.
A general prevention note
Most pest problems on melastomes trace back to stress from incorrect watering or low humidity rather than the plant being particularly pest-prone on its own. Getting the basics right — covered in our general care guide — does more to prevent pest issues than any reactive treatment.