Delphastus pusillus
Encyclopedia
Delphastus pusillus is a small ladybird beetle
which preys on all species and stages of whitefly
, but prefers eggs
and nymphs
. The adults are small ( in), shiny, black beetles. Newly-emerged adults are pale-brown to almost white. They eventually turn black with a brown head. The eggs are 0.2 mm long, clear and twice as long as they are wide. The elongate larvae are pale yellow.
eggs, which makes it easier for the young larvae to find a food source. Each instar lasts 1½–3 days. D. pusillus pupates on lower leaves, in leaf litter, or in other protected locations, often in groups. The pupa
l stage lasts approximately 6 days. Development from egg to adult takes approximately 3 weeks at 80–85°F.
and alternately sucking and regurgitating the internal contents to digest and consume it. Adult females feed more on eggs and first instar
s than on later stages. They are strong fliers that will migrate to areas that contain high densities of whiteflies. D. pusillus is most effective at high whitefly densities. Since adult female beetles must feed on over 200 eggs per day in order to reproduce, it may be of limited benefit in greenhouses where whitefly
populations are low. Both adult and larval beetles avoid feeding on whitefly nymphs parasitised by wasp
s such as Encarsia formosa
and Eretmocerus eremicus when the wasps are in later stages of development.
Coccinellidae
Coccinellidae is a family of beetles, known variously as ladybirds , or ladybugs . Scientists increasingly prefer the names ladybird beetles or lady beetles as these insects are not true bugs...
which preys on all species and stages of whitefly
Whitefly
The whiteflies, comprising only the family Aleyrodidae, are small hemipterans. More than 1550 species have been described. Whiteflies typically feed on the underside of plant leaves.-Agricultural threat:...
, but prefers eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
and nymphs
Nymph (biology)
In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...
. The adults are small ( in), shiny, black beetles. Newly-emerged adults are pale-brown to almost white. They eventually turn black with a brown head. The eggs are 0.2 mm long, clear and twice as long as they are wide. The elongate larvae are pale yellow.
Life cycle
Female beetles live for about 2 months, during which time they lay 3 to 4 eggs per day; male beetles live for 1½ months. The females generally lay their eggs within clusters of whiteflyWhitefly
The whiteflies, comprising only the family Aleyrodidae, are small hemipterans. More than 1550 species have been described. Whiteflies typically feed on the underside of plant leaves.-Agricultural threat:...
eggs, which makes it easier for the young larvae to find a food source. Each instar lasts 1½–3 days. D. pusillus pupates on lower leaves, in leaf litter, or in other protected locations, often in groups. The pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
l stage lasts approximately 6 days. Development from egg to adult takes approximately 3 weeks at 80–85°F.
Use in biocontrol
Both larvae and adults are active predators that can consume numerous eggs or nymphs each day. An adult Delphastus takes no longer than half a minute to handle a whitefly egg, and devours up to 160 eggs or 12 large nymphs daily. A larva consumes 1000 whitefly eggs (less if it also eats whitefly nymphs) during its entire development. Adults and larvae feed by piercing the insect with their mouthpartsInsect mouthparts
Insects exhibit a range of mouthparts, adapted to particular modes of feeding. The earliest insects had chewing mouthparts...
and alternately sucking and regurgitating the internal contents to digest and consume it. Adult females feed more on eggs and first instar
Instar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
s than on later stages. They are strong fliers that will migrate to areas that contain high densities of whiteflies. D. pusillus is most effective at high whitefly densities. Since adult female beetles must feed on over 200 eggs per day in order to reproduce, it may be of limited benefit in greenhouses where whitefly
Whitefly
The whiteflies, comprising only the family Aleyrodidae, are small hemipterans. More than 1550 species have been described. Whiteflies typically feed on the underside of plant leaves.-Agricultural threat:...
populations are low. Both adult and larval beetles avoid feeding on whitefly nymphs parasitised by wasp
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
s such as Encarsia formosa
Encarsia formosa
Encarsia formosa is a species of wasp and a well known parasitoid of greenhouse whitefly. The tiny females are black with a yellow abdomen and opalescent wings. There are many fewer males than females...
and Eretmocerus eremicus when the wasps are in later stages of development.