Short answer
Look closely before deciding a bug needs anything done about it, because the most alarming insect on the plant is often a predator working for you. Lady beetle larvae look like tiny dark alligators with orange markings and eat more pests than the adult beetles do. Aphids crowd the newest growth and a strong spray of water knocks them off. Bumps that never move are scale insects, a faded speckled leaf with fine webbing is spider mites, and a cloud of tiny white insects lifting off when the plant is touched is whiteflies. Sticky, shiny leaves below any of them are honeydew, the trail most of these leave behind.
Listed in the order they are worth ruling out. It is normal for more than one of these to be happening at once, so work down the list rather than stopping at the first match.
First on the list because the most alarming looking insect on a plant is often the predator eating the actual pests. Lady beetle larvae look nothing like the adult beetle, and published guidance says they are commonly misidentified as a pest, which is exactly the mistake worth preventing here.
What to check first
Look at the body shape. A long, flattened body that tapers at the back end, dark with orange, white or red markings and sometimes small spines, crawling near clusters of much smaller soft-bodied insects, is a lady beetle larva at work.
Aphids gather where the tissue is softest, so the crowd forms on shoot tips, flower buds and the undersides of the youngest leaves while the older leaves stay clear. A sticky shine on the foliage below the crowd is the second signal.
What to check first
Check two or three shoot tips and the undersides of the newest leaves. Clusters of small, soft-bodied, slow insects, in almost any color, packed onto the newest growth and not the old, settle it.
Scales barely read as insects at all. They sit as small waxy or shell-like bumps along stems and leaf undersides, often matching the bark closely enough to go unnoticed, and the adults stay fixed in one spot for the rest of their lives.
What to check first
Watch one of the bumps for a minute, then nudge it with a fingernail. An adult scale never walks away, though it can be scraped loose, and rows of matching bumps lined along a stem or leaf vein are the pattern to look for.
Spider mites are usually found from their damage rather than seen, because they are small and often difficult to see with the unaided eye. The leaf takes on many small light flecks, a speckled, faded look, and hot dry weather is their season.
What to check first
Hold a damaged leaf up to the light and look for fine pale speckling across the surface, then check the undersides and the joints where leaf meets stem for a fine silky web, which comes with heavier infestations.
This one identifies itself the moment the plant moves. When a heavily infested plant is disturbed, white clouds of winged adults fly into the air, flutter briefly, and settle back onto the undersides of the leaves.
What to check first
Give the plant a gentle shake and watch what lifts off. Tiny powdery white insects that resemble small moths rising together and settling back under the leaves is this and nothing else on the list.
Still not sure
This is exactly what your county Extension office answers, for free. They are the local horticulture experts for your area, they know what is going around this season where you live, and they will look at a photo.
Find your local Extension officePollinator Patch gives you watering and seasonal care for the plants you already own, written for your region rather than for gardening in general.