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Yarrow aphidOn this page: Identification & Distribution Biology & Ecology Other aphids on the same host
Identification & Distribution
Apterae of Macrosiphoniella millefolii are of moderate size, green and wax powdered except for a spinal stripe on the abdomen and antesiphuncular spots (cf. Macrosiphoniella usquertensis, which are brownish with a thick coating of greyish wax except for clearly defined patches on the mid-dorsum and around the bases of the siphunculi). Their antennae, siphunculi and cauda are black. The tibiae and femora are mostly black except for the basal part of the front femur which is brown (cf. Macrosiphoniella ptarmicae, whose tibiae a paler middle section). The antennae are 1.0-1.2 times as long as the body with the terminal process 3.7-4.3 times the length of the basal part. Dark sclerites are present on the sides and just in front of the siphunculi. There are numerous long body hairs on the dorsum positioned on dark scleroites, some of which may be fused into larger sclerites (cf. Macrosiphoniella tanacetaria, which does not have dorsal abdominal hairs arising from dark scleroites). The siphunculi are 0.8-0.9 times the length of the cauda (cf. Macrosiphoniella sejuncta, which has siphunculi 1.7 to 2.2 times the length of the cauda, and Macrosiphoniella tapuskae, which has siphunculi 1.8-2.3 times the length of the cauda). The body length of adult Macrosiphoniella millefolii apterae is 2.1-3.6 mm.
Alatae and immatures are similarly pigmented to the apterae, although the alatae seem to have rather less wax. The clarified slide mounts below are of adult viviparous female Macrosiphoniella millefolii : wingless, and winged.
The yarrow aphid mainly feeds on yarrow (Achillea millefolium), but it has been found on many other Achillea species, as well as on daisies (Leucanthemum), tansies (Tanacetum) and mayweeds (Tripleurospermum spp.). It does not host alternate, but does have a sexual stage in its life cycle. Macrosiphoniella millefolii is common and widespread in Europe into Asia and has been introduced into North America.
Biology & Ecology:
Overwintering eggs, laid on the stems of yarrow (Achillea millefolium) the previous autumn, hatch in spring to give fundatrices. These reproduce parthenogenetically giving birth to live young which mature and reproduce in turn. By mid-June there can be dense colonies of Macrosiphoniella millefolii living on the flower stems of their host plant (see picture below).
Lozzia et al. (2013) looked at the pattern of dispersion of Macrosiphoniella millefolii on Achillea collina, a medicinal plant grown for commercial purposes. The coefficients of Taylor's power law indicated aggregated distributions.
The alates are the dispersive phase of the species, and spread to other hosts at the right plant growth stage.
Populations can reach high levels in summer, although predation and parasitism (see natural enemies below) take a heavy toll.
From September onwards increasing number of sexuales develop. Male Macrosiphoniella millefolii are readily distinguished by their pinkish-red coloration.
Like most (but not all) Macrosiphoniella species, the males are winged.
After mating oviparae deposit their eggs on the yarrow stems.
The colour of Macrosiphoniella millefolii is thought to mimic the colour of the flower structures which may provide some protection from some natural enemies such as birds (Hille Ris Lambers, 1938).
Interspecific competition / association
It is not unusual to find other species mixed in with colony - for example the picture below shows a dense colony of Macrosiphoniella millefolii with a single light yellow-green Myzus ornatus in the middle.
Morlacchi et al. (2011) compared the development of the polyphagous aphid Myzus persicae, considered a generalist, and the oligophagous aphid Macrosiphoniella millefolii, considered a relative specialist, on yarrow (Achillea collina). The wingless viviparae of the two species differed in the immature developmental time and survival, and in adult fecundity and life span. At high temperatures, the intrinsic rate of increase (rm) as an overall indicator of performance tended to be higher for the generalist than for the specialist aphid species, while the opposite appeared to occur at low and medium temperatures.
Lozzia et al. (2013) also looked at the population dynamics and economic impact of Macrosiphoniella millefolii on Achillea collina. They found indications for an influence of the plant and a possibly limited effect of natural enemies on aphid infestations.
We have found high levels of parasitism of Macrosiphoniella millefolii. The braconid above (probably Aphidius absinthii) was found attacking Macrosiphoniella millefolii in Dundreggan, Scotland. Starý & Havelka (2008) recorded two Aphidiid species in the Czech Republic parasitizing Macrosiphoniella millefolii, Aphidius absinthii and Ephedrus niger.
In southern England the most frequent predators we have found active in Macrosiphoniella millefolii colonies are syrphid larvae.
We have not identified the larva pictured first above, but the second appears to the larva of Syrphus ribesii, a common aphidophagous syrphid. Colonies later in the year are frequently littered with the remains of aphids which have been sucked dry by the marauding syrphid larvae.
Coccinellid larvae also predate Macrosiphoniella species. The picture below shows a larva of the fourteen-spot ladybird (Propylea quattuordecimpunctata) that had been recently feeding on a colony of Macrosiphoniella millefolii on Achillea millefolium.
Other aphids on same host:
The normal host of Macrosiphoniella millefolii is yarrow (Achillea millefolii) but it also occurs on 15 other Achillea species (Achillea ageratum, Achillea alpina, Achillea atrata, Achillea colina, Achillea crithmifolia, Achillea distans, Achillea erba-rotta, Achillea filipendula, Achillea ligusta, Achillea nabelki, Achillea nobilis, Achillea ptarmica, Achillea ptarmicifolia, Achillea tomentosa, Achillea umbellata).
Macrosiphoniella millefolii feeds on one species of Leucanthemum (Leucanthemum vulgare).
Macrosiphoniella millefolii feeds on 3 species of Tanacetum (Tanacetum millefolium, Tanacetum parthenium, Tanacetum vulgare. ).
Macrosiphoniella millefolii feeds on 1 species of Tripleurospermum (Tripleurospermum inodorum).