Cave-dwelling flies in Central Europe: adaptation to environment, especially to low temperatures (Diptera, Nematocera: Trichoceridae et Sciaridae)

Summary

For Trichocera maculipennis Meig. and Trichocera regelationis (L.) (Diptera, Nematocera: Trichoceridae), and for Bradysia forficulata (Bezzi) (Diptera, Nematocera: Sciaridae), the total length of development (duration of one generation), and of pupal development alone, plotted against temperature, are described by hyperbolic equations. The derived lower limits (zero points) for total development are-1.5° C for T. maculipennis,-2.9° C for T. regelationis and-0.3° C for B. forficulata. The corresponding points for pupal development are-3.6° C,-2.5° C and +0.5° C. At least for several single stages development is proved to occur at temperatures slightly below zero for both Trichocera species. Furthermore the upper limits for development are reached at relatively low temperatures: +18° C for T. maculipennis, between +16 and +17° C for T. regelationis and +20° C to +22° C for B. forficulata.

B. forficulata inhabits caves exclusively, while the Trichocera species are wide spread field species, especially in northern Europe. The similarity of all characteristics of development investigated in all three species suggests that the field populations of Trichocera are very well “preadapted” to life in Central European carstic caves.