Psyllids, aphids, scale insects and whiteflies (Order Hemiptera, suborder Sternorrhyncha)
What do psyllids, aphids, scale insects, and whiteflies look like?
An example of an aphid. Photo: R Mascord © Australian Museum.
Psyllid. Illustration: A Howells © Australian Museum.
- Size:
- 1 mm - 40 mm in length.
- Body:
- Psyllids, whiteflies and male scale insects are generally widest at the wing attachment (wide shoulders), abdomen tapered or globular.
- Aphids are blob-like.
- Mealybugs look like a dome with segments.
- Lerp insects (immature psyllids) and female scale insects are larvae-like but their waxy coating can come in a wide range of shapes.
- Antennae:
- Thread-like, length variable.
- Eyes:
- Large and widely separated.
- Often absent in scale insects and other non-moving species.
- Mouthparts:
- For piercing and sucking, do not have visible palps (look like a chain of beads).
- Very small tube, thorn-like in appearance and appearing to come from chest.
- A small number of species have reduced mouthparts that maybe difficult to see, or retractable tubular mouthparts that are hidden in the head when not in use.
- Wings:
- One or two pairs if present.
- Male scale insects have membranous forewings with only one or two veins, hindwing absent or greatly reduced.
- Both pairs of whitefly wings are membranous, clear or partially see-through with one or two veins.
- Both pairs of psyllid wings are membranous, often covered with white waxy scales.
- At rest wings are held tent-like over body for all groups.
- Limbs:
- Six legs short and stocky.
- Some female scale insects lack legs.
- Abdomen tip:
- Cerci (tails) absent.
- Male scale insects may have a single spike or waxy filaments.
Where are psyllids, aphids, scale insects and whiteflies found?
- On the leaves or young stems of plants.
- In ant nests.
- In galls, which they create.
What do psyllids, aphids, scale insects and whiteflies do?
- Some are solitary but most form groups around a common food source.
- When disturbed they jump, run away, remain still or emit an chemical informing others of danger.
- Most lerp and female scale insects are fixed to a plant surface. They hide themselves under waxy or sugary secretions, which harden and form a protective shield. These shields are highly variable in shape, with dome-like to scallop-like shells.
- They are primarily sap feeders.
- Many, especially aphids and mealybugs, are tended by ants, which drink the honeydew they exude.
- Some produce eggs but some such as aphids produce live young. Some do not mate and produce only female offspring.
- They are active during the day or night.
What looks similar?
- Psocids are easily confused with psyllids. Psocids maybe distinguished by their large bulging nose, long antennae, wing veins that form 'S-shaped' lines, long slender legs and they usually run or fly away when disturbed rather than jump.
- Flies can be confused with male scale insects as they both have only one pair of functional wings and another pair that are reduced to haltere-like structures. However, male scale insects have only two or three veins in their wings, the haltere-like structures are not club-like and they often have a tail of waxy filaments. Flies never have this combination of characters.
