Biology, images, analysis, design...
|"It has long been an axiom of mine that the little things are infinitely the most important" |
Tansy aphidOn this page: Identification & Distribution Biology & Ecology
Identification & Distribution:Macrosiphoniella tanacetaria apterae (see first picture below) are large wax powdered green or pinkish-brown aphids. The antennae are black including the base of the third segment (cf. Macrosiphoniella artemisiae which has the base of antennal segment 3 brown). The legs, siphunculi and cauda are also black. There are no body hairs on dark scleroites. The antennae are 1.0-1.3 times the body length with the terminal process 2.9-3.5 times the length of the base of the last antennal segment. The siphunculi are 0.1-0.2 times the body length and 0.6-0.9 times the length of the cauda. The body length of apterae is 3.2-4.1 mm. The female alate (see second picture below) is much like the Macrosiphoniella tanacetaria aptera.
The picture below shows a Macrosiphoniella tanacetaria alate vivipara in alcohol.
The clarified slide mounts below are of adult viviparous female Macrosiphoniella tanacetaria : wingless, and winged.
The tansy aphid spends it entire lifecycle on tansy (Tanacetum spp.), chrysanthemum (Chrysanthemum spp.) and mayweed (Matricaria spp.) Colonies occur on upper parts of stem and between the flowers. Eggs are laid on the stem and withered leaves. Macrosiphoniella tanacetaria is common and widespread throughout Europe extending into North Africa, parts of Asia and the Americas.
Biology & Ecology:
There are two colour forms of Macrosiphoniella tanacetaria, green and pink. We have found the green form to be more common than the pink.
Masssonnet et al. (2002) looked at the pattern of dispersion of Macrosiphoniella tanacetaria on Tanacetum. A tansy plant (termed a genet) consists of many individual shoots (termed ramets). Macrosiphoniella tanacetaria was found to cluster at three spatial scales: at the level of ramets, at the level of genets and at the level of sites. At all these levels persistence is low - average survival time of aphid 'populations' on ramets is less than 2 weeks, on genets less than 4 weeks and probably only a few years in sites.
Stadler (2004) studied Metopeurum fuscoviride, Brachycaudus cardui, Aphis fabae and Macrosiphoniella tanacetaria. He found that numbers of the various species changed significantly depending on the quality of the host plant and the presence / absence of attending ants. The obligate myrmecophile, Metopeurum fuscoviride, was abundant on high-quality plants, while the unattended Macrosiphum tanacetaria did best in poor quality patches.
Loxdale et al. (2011) focused on the spatial and seasonal metapopulation structure and dynamics of Macrosiphoniella tanacetaria and Metopeurum fuscoviride. They showed that the two species rarely occurred together on the same plant at the same time, possible because of disturbance of Macrosiphoniella by the ants. Both species showed extreme genetic heterogeneity within a metapopulation structure. Indeed the number of genotypic clusters found for tansy aphids in an 80 square km area was similar to that found globally for the pest aphid Myzus persicae.
We have also found mixed species populations of Macrosiphoniella tanacetaria with other aphid species. The picture above shows an alate tansy aphid with a nymphs and (less obviously) an aptera and at least three Myzus ornatus. The latter species shows extremely good cryptic colouration against the green stem of tansy.
The honeydew produced by Macrosiphoniella tanacetaria tends to have little or no melezitose - a sugar specially attractive to ants (Fischer & Shingleton (2001) ) - so it is not tended by ants. This results in an accumulation of honeydew around the large colonies of aphids which attracts large numbers of insects other than ants, especially vespids. The Vespula, first image above, is gleaning the honeydew from the leaves under the colony. The Vespula, second above, has been killed by a crab spider.