Pinus mugo
Many species of Xyelidae facultatively diapause for several years. In "Xyela alpigena" and "Xyela obscura" a diapause of at least two years is obligate. This strategy might have evolved to ensure well developed cones are available for oviposition: the host plants "Pinus cembra" and "Pinus mugo" produce cones very irregularly in the subalpine zone of the European Alps.