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Identification & Distribution:Apterae of Macrosiphoniella millefolii are of moderate size, green and wax powdered except for a spinal stripe on the abdomen and presiphuncular spots. The antennae, siphunculi and cauda are black; the legs are mostly black except for the basal part of the front femur which is brown. 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 these may be fused into larger sclerites.
The antennae are 1.0-1.2 times the body length with the terminal process 3.7-4.3 times the length of the basal part. The siphunculi are 0.12-0.15 times the length of the body and 0.8-0.9 times the caudal length. The picture below is a micrograph of an aptera of Macrosiphoniella millefolii in alcohol.
The clarified slide mounts below are of adult viviparous female Macrosiphoniella millefolii : wingless, and winged.
The yarrow aphid does not host alternate and feeds on yarrow (Achillea millefolium). It has a sexual stage in its life cycle. It is common and widespread in Europe and North America.
Biology & Ecology:
The first picture below shows a dense colony of Macrosiphoniella millefolii on the flower stem of a yarrow plant.
The aphids in the colony above are of mixed age from the smallest I/II instar nymphs to the larger IV instar nymphs. Those with wing buds are destined to become alates. The colour of Macrosiphoniella millefolii is thought to mimic of the colour of the flower structures which may provide some protection from some natural enemies such as birds (Hille Ris Lambers, 1938 ). 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.
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 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 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 also found high levels of parasitism of Macrosiphoniella millefolii. The braconid above (probably Aphidius absinthii) was found attacking Macrosiphoniella millefolii in Dundreggan, Scotland. Starư & Havelka (2008) recorded two Aphidiid species in the Czech Republic parasitizing Macrosiphoniella millefolii, Aphidius absinthii and Ephedrus niger.
Coccinellid larvae also predate Microsiphoniella species. The picture above shows a larva of Coccinella 14-punctata that had been recently feeding on a colony of Macrosiphoniella millefolii on Achillea millefolium.