| Popis: |
Dianemobius fascipes is a wing-dimorphic cricket, developing long wings under long-day and crowded conditions at 28°C. Even under these conditions, however, severance of appendages in the nymphal stage exerted a micropterizing effect. A similar, though less pronounced, effect was obtained by exposure to heat (40°C) or cold (0°C) for 1 day. The period sensitive to such stresses ranged from the 3rd to the last (6th) nymphal instar 5 days before adult eclosion. The antepenultimate (4th) and penultimate (5th) instars were the most sensitive. Micropterous adults obtained by leg severance could be classified into 3 categories defined by discontinuous variation in wing length. These represent 3 descending steps of micropterization with increased age at the time of surgery during the sensitive period. It is inferred that the macropterous and micropterous morphogeneses bifurcate before the 2nd day of the penultimate instar, after which the surgery produced intermediate wing forms. Severance of the leg just before or after adult eclosion accelerated shedding of hindwings. Thus, injury or other stresses can modify a presumptive disperser into a non-disperser during development. |
