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Solitary birch aphidOn this page: Identification & Distribution Biology & Ecology Life cycle Rarity Other aphids on the same host
Identification & Distribution:
Adult winged forms of Monaphis antennata are green, with very long thick antennae that are black except at the base. The terminal process of the antennae is nine times as long as the base of the last antennal segment. Their siphunculi are very short with a flange. The cauda is tongue-shaped and not constricted. The forewing of the alate has an elongate dark pterostigma (see first picture above). The body length of an adult Monaphis antennata is 3.3-4.3 mm.
Immature Monaphis antennata (see second picture above) are cryptic, and usually lie along the mid-ribs on the upper sides of leaves.
Monaphis antennata live solitarily on birch (Betula species). They migrate to the undersides of the leaves for the final moult. Sexual forms occur in September-October. Monaphis antennata is found in Europe, eastward across Asia to Siberia, China and Japan.
Biology & Ecology:
The overwintering eggs of Monaphis antennata presumably hatch not long after budburst in spring, but we have not found the aphids in the field till July/August. They were present at two locations in Britain, Burton Pond Nature Reserve in West Sussex and Selwyn's Wood Nature Reserve in East Sussex. At Burton Pond female viviparae were depositing nymphs on the birch leaves as shown below. The long curved antennae of the nymphs are especially distinctive, and enable one to identify even very young nymphs as being of this species.
In the pictures above the female is (unusually) depositing her nymph on the undersurface of the leaf, perhaps because that surface was oriented upwards to enable illumination for photography. Monaphis antennata nymphs are normally found on the upper sides of the leaves and Hopkins & Dixon (2000) showed experimentally that fourth instar nymphs will settle on the upper side of the leaves if leaves are orientated naturally. Interestingly, if leaves are orientated with the undersurface upwards around half the aphids still prefer the former upper surface, suggesting that the aphid is responding to a leaf feature rather than just light or gravity.
Hopkins & Dixon (1997) thought that the upper surface of birch leaves (where most birch aphids live) provided an enemy-free space compared to the under surface. They demonstrated that Monaphis antennata nymphs occupying the upper surfaces of the leaves - the normal feeding position - were less likely to be attacked by coccinellid larvae than those occupying the under surfaces. Whilst this is the case for 'random walk' predators such as coccinellid larvae, the upper surface does not provide a predator-free space when considering predators that search visually for prey - such as birds and vespid wasps - quite the opposite in fact. These presumably provided the selective pressure for development of the excellent crypsis of Monaphis antennata nymphs.
Sexuales of Monaphis antennata develop in autumn. Males can be readily recognised as such since they are red, smaller than viviparae and, when mature, alate (see picture below of an immature male).
Copyright Christophe Quintin under a Creative Commons Attribution-NonCommercial 2.0 licence
Copyright Claude Pilon, by permission, all rights reserved.
The tergites from mesonotum to to abdominal tergite VII each have a narrow pale brown sclerotic band, those on the mesonotum and abdominal segments VI-VII occupy the whole width of tergites, those on the remaining segments are shorter and do not reach the body sides. The antennae are long and black, without secondary rhinaria. The hind tibiae are dark brown, and distinctly swollen with about 60-80 pseudosensoria (Stroyan, 1977).
After mating the ovipara lays its eggs, but it does not seem to be known whether they lay them on the leaves or on the twigs and branches. The eggs hatch the following spring to give the fundatrices.
So how rare is Monaphis antennata?
In Poland Labranowski & Soika (2011) reported that Monaphis antennata was the least common aphid species on birch in ornamental plants nurseries. But Durak & Wojciechowski (2008) found Monaphis antennata subdominant in two types of birch woodland, and more common than several species including Calaphis flava, Callipterinella tuberculata and Hormaphis betulae. In Turkey Senol et al. (2014) found Monaphis antennata on a birch tree in the city centre and noted that "all individuals were alatae and heavily colonized the leaves of the tree".
In Britain Monaphis antennata is generally considered to be a rare aphid (Dixon & Thieme, 2007). Hopkins et al. (1998) note that it is 'always' found at low densities on individual hosts and has low local abundance, at least in comparison with another birch-feeding aphid, Euceraphis betulae. In southern England we have found Monaphis antennata less common than Euceraphis species and Symydobius oblongus, but more frequent than several species including Glyphina spp., Callipterinella calliptera and especially Hamamelistes betulinus.
Other aphids on same host:
Monaphis antennata has been recorded from at least 6 Betula species (Betula maximowicziana, Betula microphylla, Betula papyrifera, Betula pendula, Betula platyphylla, Betula pubescens).
Blackman & Eastop list about 72 species of aphids as feeding on birches worldwide, and provides formal identification keys for aphids on Betula.