British distribution: Throughout Britain.
Classification and identification
The genus Myrmica is one in which the narrow waist ("pedicel") consists of two distinct segments, i.e., technically, they possess a "postpetiole" as well as a "petiole". Leptothorax is a similar genus with at least one common species, but which differs in the shape and structure of the antennae. Other well known genera such as Formica and Lasius have the single petiole.
Myrmica ruginodis belongs to the Myrmica rubra group of species – a difficult group needing careful attention to critical characters for identification. Important features are the gentle curve at the base of the antenna (not distinctly angled) and the pair of propodeal spines projecting from the rear of the alitrunk (the main part of the thorax). In M. rugodinis. these spines are relatively long – as long as the distance between their tips. However, for fuller separation of Myrmica species, reference must be made to identification handbooks such as Bolton & Collingwood (1975) and/or Skinner & Allen (1996). Both books list eight British Myrmica species. M. rugodinis is one of the most common, occuring throughout Britain and especially in the north, forming nests in tree trunks and rotting wood, under stones in woodland and in similar, somewhat sheltered sites.
Shown above are flowers of a yellow variant of Common Broomrape (Orobanche minor), a species in which the whole of the upper exterior of the plant is covered with minute sticky ('glandular') hairs. The ants cannot cross over these hairs. However, as shown in the photograph, a leaf of Ribwort Plaintain is just touching a flower and the ants are able to use it as a bridge to reach the lip of the flower (which, since it is the landing platform for the intended flying pollinators, does not have the sticky hairs). Showing the usual social organisation of ants, a small number of workers remained firmly holding the leaf in contact with the broomrape flower, while a succession of other workers raided the nectar.
It should be noted, of course, considering ants in general, that while they may be disadvantageous to plants by stealing nectar or tending aphids, they may also act to protect the plants from various herbivores. Some plants have non-floral nectaries that may encourage ants, and a number of more specific, mutualistic plant-ant associations are known, involving tropical ant species.
Ants, including Myrmica species, are also known for tending the larvae of 'blue' butterflies of the family Lycaenidae, sometimes taking them into their nests. The Large Blue butterfly (Maculinea arion), now extinct as a native in Britain, was particularly dependent on Myrmica sabuleti, an ant of warm, open banks. Caterpillars are able to secrete nectar-like drops and possibly fool the ants into thinking they are the ants' own larvae, though once taken into the ant nest, the caterpillars feed on the ant larvae. The current reintroduction programme for the butterfly recognises the importance of maintaining the ant species in the chosen sites.