Adelgidae
Aphididae
Pemphigidae
Phylloxeridae
and several more
Aphids (superfamily Aphidoidea) are small plant-feeding insects with 'piercing-sucking' mouthparts (stylets). Similar to related superfamilies they passively feed on sap of phloem vessels in plants. This sap is under high pressure and forced into the food canal once a phloem vessel is punctured. They actively 'drink' (suck) from xylem vessels when thirsty. There are several families and numerous genera. They are generally soft-bodied with long thin legs; adults have lacy transparent wings. Most of the aphids one sees in a plant infestation are juveniles.
Many aphids are serious pests in agriculture and forestry, and an annoyance for gardeners. Important natural predators include ladybirds, hoverfly larvae and lacewings.
Some species of ants "farm" aphids, supplying them with leaves to eat, and eating the honeydew that the aphids secrete. Many aphids are host to an endosymbiont bacteria, Buchnera , which synthesizes the essential amino acids that are absent in the phloem that the aphids eat.
Genera include Adelges , Aphis, Brevicoryne , Daktulosphaira (Vine Phylloxera), Elatobium , Eriosoma , Macrosiphum , Marchalina, Metopolophium , Myzus , Pemphigus , Phylloxera, Rhopalosiphum , Tetraneura and many more.
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