The larvae feed on Apiaceae, particularly Pimpinella saxifraga, Pastinaca sativa and Peucedanum sp. More rarely the caterpillar lives on Rutaceae (e.g. Dictamnus albus or Citrus). In Southern Europe Foeniculum vulgare is a very important host plant as own larval observations show (Samos, Rhodes, Crete, Spain, Portugal).
Papilio machaon can live in a broad variety of open and half open habitats. It is also found on
larger clearings. But it can reproduce only where the area is not mown more than once or twice a year, so not in todays intense agricultural grassland. The highest larval concentrations usually occur in sunny limestone grasslands with Pimpinella saxifraga.
Some populations have specialized on certain types of habitat, such as the extremely local population in England that only live in fens.
Papilio machaon occurs in Central Europe mostly in two, rarely three generations per year. In Southern Europe the third generation is more regular. The pupa overwinters. The butterflies are on the wing from April to September and are especially in the spring often observed when hilltopping (males congregate on hilltops for courtship).
The larvae feed from late April or May to October, in Southern Europe even in November (N-Portugal, 02/11/2013, near Caminha).
Endangerment: regionally endangered or decreasing
In cleared, inhospitable landscapes as in large parts of Northern Germany, even this actually quite undemanding species becomes more and more rare. Where nutrient-poor grasslands still exist as in the Jura mountains, caterpillars are sometimes observed in larger numbers.
The caterpillar may also occur in gardens on carrots, fennel, dill, etc., where they should be left as it causes no real damage.
Papilio machaon occurs from Northwest Africa across Europe (in England only very locally) and Asia to Japan and is also found in North America (holarctic distribution type).