Sycamore aphid - June 2021
There are more than 500 aphid species in Britain. Some feed on only one or two plant species, but others can be found on a wide range of plant hosts. The Sycamore is an introduced non-native tree and as such has very limited insect fauna associated with it, reportedly only hosting an average of 15 species, where the Oak will support up to 280 species! However one species of insect is extremely loyal to the Sycamore and at this time of year is so prolific, it is hard to find a tree without a colony of Sycamore aphids.
This aphid spends all year on Sycamores, overwintering as eggs placed in bark crevices and behind buds. The eggs hatch in early spring, and there is a migration in late spring/early summer to new Sycamore trees. All the adults are winged, and range in size from 3.2 to 4.3 mm long. They have red eyes, a brown thorax, and a pale green abdomen. The upper surface of the abdomen has up to 5 or 6 variably developed dark cross-bars. Early in the year these cross bars may be reduced or absent altogether. Nymphs lack wings and are all green.
All aphids are notoriously hated by gardeners, or anyone trying to grow anything as they are a small bug which feeds on the sap of plants, weakening the plant or even killing it. Aphids are a primary food source for beneficial insects, in their larval stage, lacewings, ladybirds and their alien looking larvae eat hundreds of aphids a day! Many aphids have a complicated relationship with ants, who herd and care for them in order to keep a much loved food in constant supply (the honeydew the aphids excrete). The unique relationship provides protection for the aphids against their predators, it has also recently been discovered the ants also prevent fungal outbreak amongst the aphid population, by removing infected bodies. Sycamore aphids are not attended by ants, but wasps can often be found gleaning their honeydew from the leaves, although they don’t offer protection as payment.