The adult insects are about 2 mm in size and have two pairs of wings and are covered with fine, white wax powder. Their eyes are separated into upper and lower halves by tissue.
Usually, they sit well protected on the undersides leaves and jump off using their hindlegs when disturbed, going into flight. The 0.25 mm long, ellipsoid eggs are anchored to the underside of young leaves with a little stem, which also supplies them with moisture.
Freshly laid eggs are white, but turn increasingly darker during their six to eight day development period (at 20 °C).
Development Phases
During the first instar, the larvae look for a spot to tap into the plant’s sap for feeding on their birth leaf and will not leave that spot.
The insects are fixed to the leaf from their second instar onwards. They insert their stylets into the phloem (in a similar way to aphids) and feed on the sugary sap taken from their hosts vascular bundles. Egg-laying females are often found on the higher, younger leaves on host plants with several levels of leaves, such as cucumbers or tomatoes; the larvae are found on the leaves on the middle section and the hatching whiteflies on the lower, older leaves.
Eggs, larvae and adult animals require fresh plants to survive and die after short periods of time when stuck on wilted leaves. Their development comprises four instars, similar to scale insects, in which they grow up to 0.8 mm. In their first instar, they can still move and have functioning extremities, which they will lose later.
All their instars are mainly translucent, showing only a few yellow spots inside their bodies. These spots are inhabited with symbiotic bacteria, which produce important vitamins for the whiteflies.
These bacteria migrate from the mother insect into the unfinished eggs during the egg development stage, thus, being transferred to the organisms of the next generation.
The last instar (pseudopuparium) looks like a tiny, minute, oval cylinder with vertical walls and is white-to-yellow in colour. The development period from the egg to the finished adult insect takes about 25 to 30 days. As a result, it is possible that several, overlapping generations develop every year.
The whitefly can only survive the winter on green plants in glasshouses or homes, as it has no hibernation form and is very susceptible to cold temperatures.
AGES - Austrian Agency for Health and Food Safety
