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Genus Brachycaudus [Macrosiphini]

Brachycaudus are rather small to medium-sized aphids which are green, dark green or ochreous-reddish. They have very low antennal tubercles and their antennae are shorter than the body. The terminal process of the last antennal segment is 3 or more times the basal part. The abdominal dorsum in apterous Brachycaudus is variably sclerotized, but frequently has an extensive dark sclerotic shield. Marginal tubercles are small or absent, and never on abdominal tergite 7. The siphunculi are short to moderate in length, nearly smooth, cylindrical or tapering, and distinctly flanged. The cauda is semicircular or helmet-shaped, shorter than its width , and with a slight basal constriction.

Brachycaudus is a genus of 50 species found mainly in the Palearctic. About 14 species have plum (Prunus spp.) as the primary host. There are species groups associated with different secondary hosts - two of the most common species use daisies (Asteraceae). Other species do not host alternate, living year round on a variety of plant species. Some Brachycaudus species still have a sexual stage in their life cycle, but most do not. Brachycaudus aphids may be attended by ants. Some are important crop or fruit tree pests.

 

Brachycaudus bicolor (Hound's tongue aphid)

The apterae of Brachycaudus bicolor (see two pictures below) are shining yellowish tinged with pink, to pale green, with separate cross bars on thoracic segments, a variably developed black patch situated dorsally on the abdomen and 2 or 3 black stripes at the tip. Their siphunculi may be pale, dusky or quite dark. The body length of apterous Brachycaudus bicolor is 2.1-2.4 mm. The light green and reddish green aphids in the photos below are likely immature Brachycaudus bicolor.

 

The hairs on abdominal tergite 8 are 30-113 μm long, much longer than the dorsal hairs on more anterior segments. Both the aptera and the alate of Brachycaudus bicolor have conspicuous flat marginal tubercles present on all segments from the pronotum to abdominal tergite 7, and spinal tubercles on the pronotum and abdominal tergites 7 and 8.

In Britain Brachycaudus bicolor is usually found in ant-attended colonies on root collars or at the bases of leaves of Hound's tongue (Cynoglossum officinale). In Europe it has been recorded on various members of the Boraginaceae. No sexual morphs have been recorded and the species overwinters as parthenogenetic forms. Brachycaudus bicolor has been found Britain, southern Europe, Egypt and parts of Asia.

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Brachycaudus cardui (Plum - thistle aphid)

Brachycaudus cardui apterae (see first picture below) are brownish-yellow, pale green or brown, with separate cross bars on thoracic segments, a large shining black spot situated dorsally on the abdomen and 2 or 3 black stripes at the tip. Their siphunculi are black, thick and cylindrical and 1.7-3.4 times the length of their cauda. The Brachycaudus cardui rostrum is long and reaches the hind coxae. The body length of apterae is 1.8-2.4 mm. Immature Brachycaudus cardui (see second picture below) often have reddish patches on a greenish background.

 

The longest hairs on abdominal tergite 8 are 85-110 μm long, and the longest hairs on the hind femur are 40-80 μm long. The length of these hairs distinguishes Brachycaudus cardui from the short-haired Brachycaudus lateralis

In continental Europe Brachycaudus cardui host alternates between various Prunus species, mainly cherry, plum and apricot, and various wild and cultivated daisies (Asteraceae) especially thistle (Carduus and Cirsium spp.) and borage (Boraginaceae). In Britain it seems to live all year round on Asteraceae. Infested leaves undergo severe curling. Dense colonies occur at the base of flower heads and on the leaves. A return migration to primary hosts occurs in autumn. The plum-thistle aphid is found throughout Britain and Europe as well as in Asia, north Africa and North America.

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Brachycaudus helichrysi (Leaf-curling plum aphid)

The adult aptera (see first picture below) on the primary host is variable in colour ranging from yellow to green to brown, often shiny with a slight wax dusting. On the secondary hosts they can be yellow, green, or almost white or pinkish. The antennae are shorter than the body with dusky tips. The dorsum of the abdomen is without a black shield. The siphunculi are pale, tapered and short - 0.8-2.0 times the length of the cauda. The cauda is pale, short and blunt. The body length of apterae is 0.9 - 2.0mm.

 

The leaf-curling plum aphid host alternates between various plum (Prunus) species (especially domestic plum and blackthorn) and a wide range of Asteraceae such as asters, chrysanthemums, yarrow and groundsel. The populations on red clover (Trifolium pratense) have been called var warei, but are not thought sufficiently distinct to warrant subspecific status. This aphid is a serious pest on fruit trees causing the leaves to roll up tightly perpendicular to their mid-rib (see second picture above).

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Brachycaudus lateralis (Short-haired thistle aphid)

Brachycaudus lateralis apterae (see first picture below) are green or reddish, with separate cross bars on thoracic segments, a large shining black spot situated dorsally on the abdomen and 2 or 3 black stripes at the tip. Their siphunculi are black, thick and cylindrical and 2.3-3.4 times the length of the cauda. The rostrum is long and reaches the hind coxae. The body length of apterae of Brachycaudus lateralis is 1.6-2.6 mm. Immatures (see second picture below) often have reddish patches on a greenish background.

 

The longest hairs on abdominal tergite 8 are 20-61 μm long, and the longest hairs on the hind femur are 10-25 μm long, much shorter than the hairs on the closely related Brachycaudus cardui This character is used to distinguish between the species (subspecies? forms?) The results of recent DNA studies suggest that Brachycaudus lateralis should only be accorded subspecific status. The alate female (not pictured) has a dorsal patch irregularly bordered, and partly broken into crossbars and smaller sclerites. There are 18-35 secondary rhinaria on antennal segment III, and none on segment IV.

Brachycaudus lateralis is usually found close to the ground on the stems and leaves of numerous Asteraceae, including chamomile (Anthemis), thistles ( Carduus, Cirsium) and ragworts and groundsels (Senecio), where they are usually attended by ants. It usually remains on Asteraceae all year, although it has been recorded host alternating to plum (Prunus). Brachycaudus lateralis is found over most of Europe.

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Brachycaudus linariae (Toadflax aphid)

Adult apterae of Brachycaudus linariae are deep blackish shiny green. Immatures are a somewhat paler green. The last two fused rostral segments range in length from 0.135 to 0.160 mm. The body length of adult Brachycaudus linariae apterae is 1.4-1.9 mm.

 

There are medium to large flat marginal tubercles on the pronotum and on some or all of abdominal tergites 1-5. Brachycaudus linariae alatae have 11-33 secondary rhinaria on the third antennal segment, 6-9 on the fourth segment and 0-2 on the fifth segment.

Toadflax aphids live on the basal parts of toadflax, especially yellow toadflax (Linaria vulgaris). Sexual morphs of the toadflax aphid have not yet been found in UK, but have been recorded in Slovakia. Brachycaudus linariae is found in parts of western and northern Europe and most of eastern Europe.

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Brachycaudus lychnidis sp group (Campion aphids)

The dorsal abdomen of apterae has an extensive solid shiny black shield with the underside red-brown. The median frontal tubercle is about as high as the antennal tubercles. The antennae are 0.6-0.8 of the body length. The legs have the fore femora pale with dorsally dark apex; the hind femora are dusky with a pale base. The tibiae are pale with the apex and base dark. The siphunculi are dark truncated conical, and the cauda is rounded or semi-oval.

The campion aphids include Brachycaudus lychnidis and Brachycaudus klugkisti both of which live all year on red campion (Silene dioica) and related species but cannot (as yet) be separated in photos. Brachycaudus lychnicola also has the same host but lives at the base of the plant - all those we have found live on the upper parts of the plant.

The species in the photo is characterized by the wax ring around the terminal abdominal segments - this was very apparent in numerous live specimens, but is not mentioned in the literature, presumably because such deposits are not apparent in prepared slide specimens.

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Brachycaudus malvae (Mallow aphid)

Adult apterae of Brachycaudus malvae are pale green with separate black cross bars on thoracic segments, and an extensive shining black sclerotic shield on the dorsum. The hairs on the third antennal segment are very short, only 0.2-0.25 times the basal diameter of that segment. The last two fused apical rostrall segments (RIV + V) are 0.165-0.190 mm in length. The siphunculi are black and cylindrical. The body length of Brachycaudus malvae apterae is 1.8-2.3 mm.

 

Abdominal tergite 8 bears 10-14 short hairs, not in a single row. Marginal tubercles are often absent; if present they are usually only on the prothorax and abdominal tergites 2-4. Brachycaudus malvae is closely related to Brachycaudus cardui  and Brachycaudus lateralis  in the subgenus Acaudus.

Brachycaudus malvae lives all year feeding on mallow (Malva) species with no host alternation. Aphid colonies are usually attended by ants. Sexual morphs have apparently not been described. The species is found in Britain, Spain, Italy, southern Russia, Ukraine and China (an odd distribution suggesting the species has been overlooked in many countries).

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Brachycaudus persicae (Black peach aphid)

Adult apterae of Brachycaudus persicae (see dark individuals in pictures below) have a shiny sclerotized dark brown or black dorsum. The black flanged siphunculi are more than 0.1 times the body length, clearly more than twice the length of the cauda and longer than the hind tarsi (distinguishes from Brachycaudus schwartzi which has markedly shorter siphunculi). The cauda is dark, short and broad. Immature stages of Brachycaudus persicae are yellowish to dark brown. The body length is 1.5-2.2 mm.

 

The fused apical rostral segments of the aptera are shorter than 0.175 mm in length. Winged spring migrants have similar coloration to the apterae, and have 23-51 secondary rhinaria on the third antennal segment, 9-21on the fourth, and 1-6 on the fifth. Brachycaudus persicae nymphs are yellowish-brown to dark brown.

Brachycaudus persicae is most commonly found in large spring colonies on young stems of peach (Prunus persica) or almond (Prunus armeniaca), often persisting into the summer on root suckers. In Europe there is some evidence of host alternation from Prunus to Orobanchaceae, but Brachycaudus persicae may remain all year on Prunus. Aphids apparently of this species are also widely distributed on peach outside Europe, including the Middle East, southern Africa, Australia, New Zealand, and North and South America.

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Brachycaudus tragopogonis (Goats-beard aphid)

Adult apterae of Brachycaudus tragopogonis are shining grey-brown to dark brown, although a dense colony appears black, The extent of dorsal abdominal sclerotization is variable, with the cross bands often divided spinally as well as intersegmentally into paired pleural patches. The siphunculi are 0.05-0.06 times as long as the body length and 1.2-1.5 times as long as the cauda. The cauda is helmet-shaped. The body length of Brachycaudus tragopogonis apterae is 1.4-2.3 mm.

 

Brachycaudus tragopogonis lives all year round on the stem and leaves of Tragopogon (goatsbeard) species with no host alternation. Oviparae and winged males appear in autumn. The species is found in southern Britain and over much of Europe, and has been introduced to South America.

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Acknowledgements

We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994)  and Blackman & Eastop (2006)  supplemented with Blackman (1974) , Stroyan (1977) , Stroyan (1984) , Blackman & Eastop (1984) , Heie (1980-1995) , Dixon & Thieme (2007)  and Blackman (2010) . We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure  provided by Blackman & Eastop (2006).

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