Recorded food plants are Lathyrus species, Vicia species, Vicia cracca, Oxytropis campestris, bird's foot trefoil (Lotus corniculatus), Oxytropis pyrenaica, Astragalus aristatus, Astragalus onobrychis, Astragalus pinetorum, black medick (Medicago lupulina), Medicago romanica, Medicago falcata, common restharrow (Ononis repens), wild thyme Thymus serpyllum, lesser trefoil (Trifolium dubium), Trifolium pratense and white clover (Trifolium repens). Flavonoids Common blues sequester flavonoids from their host plants and allocate these pigments that are UV-absorbing into their wings. These flavonoid pigments in females attract males. Males who patrol areas of suitable habitats while searching for virgin females stop and inspect females who have flavonoid pigments in them. This may be due to the fact that flavonoid pigments that have UV absorption increase color saturation on females and allow females to be more conspicuous. There are also some other advantages of sequestering flavonoids, including the protection of eggs from adverse UV chemical reactions, as the butterflies will absorb the UV rays, and the flavonoids can offer a chemical defense against predators or pathogens. Flavonoid sequestration is much more effective when coming from natural host plants than from experimentally offered diets. Females sequester about 60% more flavonoids than do males. This richness in females may increase visibility, but could also confer information about feeding history, and consequentially the quality of potential mate. Flavonoid sequestration is an important component of intraspecific visual communication and sexual signaling in Polyommatus butterflies. Parental care Oviposition During oviposition, females must locate a potential host plant and evaluate its suitability as the host plant for oviposition. P. icarus uses visual cues to conduct this task. Females use several plants in the family Fabaceae as larval host plants, many which could also potentially function as nectar sources. P. icarus prefers plants with flowers over plants without, and prefers to oviposit near the flowers. Life cycle As a caterpillar, the common blue eats leaves. As an adult butterfly, it feeds on wildflower nectar and excrement. The adult lives 3 weeks. Males are often very obvious as they defend territories against rivals and seek out the more reclusive females. In the south of Britain there are two broods a year, flying in May and June and again in August and September. Northern England has one brood, flying between June and September. In a year with a long warm season, there is sometimes a partial third brood in the south flying into October. Eggs The egg stage lasts for