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Pear-hogweed aphidIdentification & Distribution Biology & Ecology Damage & Control
Identification & Distribution:The plump-bodied fundatrices of Anuraphis subterranea are dark brown. Anuraphis subterranea antennae are short. The terminal process of the last antennal segment is longer than the base of that segment. There are large marginal tubercles on abdominal tergites 1-7, and often also spinal tubercles. Anuraphis subterranea siphunculi have close-set rows of fine spinules. The cauda of Anuraphis subterranea is helmet-shaped, not longer than its basal width in dorsal view. Their offspring are brownish-green to brownish-black (this feature distinguishes Anuraphis subterranea from Anuraphis farfarae whose nymphs are yellowish-green) and these all develop to brown emigrant alates.
Anuraphis subterranea alates have a broad dark patch on abdominal tergites 4-6. This patch is almost solid in spring migrants but is smaller with a large window in alates produced on the secondary host. (Anuraphis subterranea host alternates.)
The clarified slide mount below is of adult wingless female Anuraphis subterranea (on primary host).
On their winter hosts, pear (Pyrus) Anuraphis subterranea fundatrices live in rolled and crumpled leaves. The living leaf tissue is turned characteristically reddish (with Anuraphis farfarae the leaf tissue usually remains green). Their summer hosts are umbellifers such as cow parsley (Heracleum sphondylium) and wild parsnip (Pastinaca sativa). Here Anuraphis subterranea live inside the lower leaf sheaths and at the stem bases. On their summer host, pear-hogweed aphid are attended by ants. Anuraphis subterranea is found throughout Europe, North Africa and eastward to Iran.
Biology & Ecology:
Brownish-black nymphs develop inside the red gall on pear. They will all develop to alates and migrate to the secondary host.
The feeding habitat on their secondary host, termed a domatium, was described by Hansen (2007). The stem-base leaf sheath is curved inwards, and the ants (usually Lasius niger) construct soil shelters on top of the domatium enclosing the aphids. This 'earth tent' blocks entry to aphid predators such as Adalia bipunctata. As an adaptation to this environment, Anuraphis subterranea has an unusually long rostrum: 0.7 times the body length.
The three-way mutualistic relationship between the aphid Anuraphis subterranea, the plant Heracleum mantegazzianum and Lasius ants has been studied experimentally by Hansen (2006). They found a positive correlation between relative plant growth, ant activity, and the number of Anuraphis subterranea. Because of the restricted domatium size, Anuraphis subterranea populations were limited in growth, and consequently the damage they inflict was limited. In contrast to the few other systems where three-partner mutualistic relationships have been described, these partners appeared to be well adapted to each other. The number of individuals of two leaf-feeding aphid species that were not attended by ants, namely Paramyzus heraclei and Cavariella theobaldi, were negatively correlated with the growth of giant hogweed in its native habitat. (In the UK giant hogweed, Heracleum mantegazzianum, is a phototoxic invasive species.)
Damage and control
The pear-hogweed aphid is not generally considered of any economic importance.