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Clover aphid, Medick aphidOn this page: Identification & Distribution Biology & Ecology Other aphids on the same host
Identification & Distribution
Aphis coronillae lives in ant-tented colonies on the basal parts of clovers and medicks (see first picture below). The adult aptera of Aphis coronillae (see second picture below) is pinkish brown to brownish green with a more or less shiny black dorsal shield and no wax powdering. The shield extends over segments 1-6 inclusive, but is weakened by membranous lines between some of the anterior segments. The shield is reticulated, a feature formerly only thought to be visible in slide mounted specimens, but also apparent in photos of the live insect. Abdominal tergites 1-4 and 7 regularly bear very protuberant, dome-shaped marginal tubercles, clearly visible in the pictures below (cf. Aphis craccivora where tergites 2-6 are usually without marginal tubercles, or rarely with 1-3 small ones). Nearly all the hairs on the legs are very short. The body length of adult Aphis coronillae apterae is 1.3-2.2 mm.
Aphis coronillae alatae (see second picture above) are reddish brown with bands on most or all abdominal tergites, that on tergite VI being broader and amalgamated with the postsiphuncular sclerites. They have 3-9 secondary rhinaria on antennal segment III, and 0-2 on segment IV. Immatures (see first picture below) range from greenish-yellow (the youngest) to reddish brown (fourth instars).
There are two subspecies with specific host-plant associations, but the morphological discriminants for the two subspecies are slight:
Most of the aphids pictured on this page are Aphis coronillae arenaria.
Aphis coronillae lives on the basal parts of certain Leguminosae / Fabaceae, especially clovers (Trifolium) and medicks (Medicago). It does not host alternate. Sexual forms appear in September. The males are mostly apterous, but are occasionally brachypterous or alate. Aphis coronillae is usually attended by and sheltered by ants. It is widely distributed in Europe, and is also found in west Siberia.
Biology & Ecology
One of the main hosts of Aphis coronillae arenaria is black medick Medicago lupulina (see picture below), a very common herb found in pastures and lawns. It is a pioneer plant often growing in disturbed ground, and is especially fond of xeric habitats such as pavements in residential areas.
We have found Aphis coronillae arenaria on many occasions between July and September on the runners of black medick or spotted medick growing in and around pavements in various East Sussex villages (see pictures above). Aphis coronillae coronillae on clover seems less common although we have found it several times. The paucity of records of Aphis coronillae is doubtless enhanced by its subterranean feeding site. The only indication of the aphids' presence is tenting with debris over infested runners by attending ants. The common black ant (Lasius niger) is usually the species that carries out the earth tenting and attends the aphids.
First and second instar Aphis coronillae (see picture below) are yellowish-green with some reddish coloration near the siphunculi.
Third and fourth instars (see picture below) are a rich reddish-brown, with a light dusting of wax in transverse bands across the dorsal abdomen.
As they develop to adults, they acquire a more-or-less shiny black dorsal shield.
The extent of this shield is somewhat variable (see pictures of two adult apterae below).
We have not yet found sexuales of Aphis coronillae but they develop in late autumn. The males are mostly apterous, but are occasionally alate or brachypterous. The oviparae have rather slightly swollen hind tibiae with fewer than 100 scent plaques (sex pheromone glands).
Baker (2009)reports finding Aphis coronillae subspecies arenaria on subterranean parts of Medicago lupulina, growing on 'brownfield' land in Cardiff Bay during summer, 2007. It was sheltered and attended by the ant Lasius niger. There are also recent reports from Switzerland (Lethmayer, 1998), West Siberia (Stekolshchikov et al., 2008) and Greece (Tsitsipis, 2007).
Other aphids on the same host
Aphis coronillae coronillae has been recorded from 7 Trifolium species (Trifolium campestre, Trifolium caucasicum, Trifolium fragiferum, Trifolium hybridum, Trifolium medium, Trifolium pratense, Trifolium repens).
Aphis coronillae arenaria has been recorded from 2 Medicago species (Medicago falcata, Medicago lupulina).