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Large blackberry aphidIdentification & Distribution Biology & Ecology Other aphids on the same host
Identification & Distribution:Amphorophora rubi apterae are pale green or yellowish green with pale siphunculi. Their antennal terminal process is usually less than seven times the length of last two segments of the rostrum. The third antennal segment bears 2-44 rhinaria with its longest hairs 26-48 µm (cf. Amphorophora gei which has the longest hairs on the third antennal segment 17-30 µm long). The siphunculi are slightly swollen on the apical part and 2.1 to 2.4 times the length of the cauda. The cauda is triangular. The body length of Amphorophora rubi apterae is 2.2-4.7 mm.
The first image below shows an apterous adult Amphorophora rubi in alcohol. The second image below shows a close-up of the swollen siphunculi.
The clarified slide mounts below are of adult viviparous females of a closely related sprecies, Amphorophora idaei : wingless, and winged, a species on raspberry that is (almost) morphologically indistinguishable from Amphorophora rubi.
The large blackberry aphid does not host alternate. It feeds on the underside of leaves of blackberry (Rubus fruticosus agg.) and related Rubus species, but not on raspberry (Rubus idaei). Amphorophora rubi is found throughout Europe and has been introduced to New Zealand.
Biology & Ecology:Life cycle
Little has been written about the biology and ecology of the large blackberry aphid (Amphorophora rubi), although it is likely in many respects to be similar to the European large raspberry aphid (Amphorophora idaei), the biology of which was reviewed by McMenemy et al. (1976). Our field records suggest that the overwintering eggs of Amphorophora rubi hatch in March to give apterae by May-June. The aphids below were found on bramble in an unheated glasshouse in mid-April.
We have found that alatae (see first picture below) start to appear somewhat earlier (mid May) than is reported for Amphorophora idaei, and then disperse to found colonies on new plants (see second picture below).
As with the raspberry aphid, the apterous nymphs and adults are very mobile, and drop from the plant when they are disturbed. This appears to be their main strategy for dealing with predators. Note by the way that the swollen siphunculi are not always very apparent in photos of the aphid, as is evident in the second picture below.
We have found parasitized Amphorophora rubi on several occasions. The picture below shows a recently mummified aphid - note especially the strands of silk holding the mummy to the leaf.
Various parasitoids have been recorded attacking Amphorophora rubi. Tomanovic et al. (2009) recorded Ephedrus lacterosus in Serbia & Montenegro. Muller et al. (1999) reported Praon dorsale, Aphidius rubi and Aphelinus abdominalis, and the hyperparasites Asaphes vulgaris, Copruna clavata and Phaenoglyphis xanthochroa.
We have not found large numbers of predators around Amphorophora rubi colonies, although the predatory bug shown below was feeding on the Amphorophora.
We have observed fungal pathogens rather more often. The image below shows an alate Amphorophora rubi killed by an Entomophthora pathogen.
We have also found larval trombidid mites on Amphorophora rubi as shown below (first picture shows mite on aphid, second picture shows mite under high magnification in alcohol):
The effect of larval trombidid mites on an individual aphid depends on the parasitic mite load and the age/size of the aphid. A single mite reduces the aphid's fecundity, but several on the same aphid may kill the host (for more information see mites on aphids ).
Other aphids on same host:
Blackman & Eastop list 10 species of aphid as feeding on blackberry (Rubus fruticosus) worldwide, and provide formal identification keys.
Of those aphid species, Baker (2015) lists 7 as occurring in Britain: Amphorophora rubi, Aphis ruborum, Aulacorthum solani, Macrosiphum euphorbiae, Macrosiphum funestum, Macrosiphum rosae and Sitobion fragariae.
Loxdale & Brookes (1989) found that electrophoresis provided an excellent way to differentiate early instars of four of these species, Amphorophora rubi, Macrosiphum funestum, Sitobion fragariae and Aphis ruborum.
Sometimes the different species form mixed species colonies as is shown below, with Amphorophora rubi (green) and Macrosiphum funestum (reddish) forming a mixed species colony on Rubus.