. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 364 M. A. RANKIN AND S. RANKIN cate the tendency to migrate in this group (Southwood and Johnson, 1957; South- wood, 1962; Dingle, 1965). Our initial tethered-flight experiments indicated that in H. convergens the duration of such flight is a reasonable measurement of willingness to migrate. A beetle that flies 30 min is very likely to fly much longer, often for several hours. Only a portion of the population will make long flights under any circumstances but the ratio of fliers to non-fliers changes throughout the year and
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 364 M. A. RANKIN AND S. RANKIN cate the tendency to migrate in this group (Southwood and Johnson, 1957; South- wood, 1962; Dingle, 1965). Our initial tethered-flight experiments indicated that in H. convergens the duration of such flight is a reasonable measurement of willingness to migrate. A beetle that flies 30 min is very likely to fly much longer, often for several hours. Only a portion of the population will make long flights under any circumstances but the ratio of fliers to non-fliers changes throughout the year and the life cycle. The times of greatest percentage of long fliers in laboratory flight tests correspond to the times of population movements to and from the aggregation sites in the field. As is true for many insect migrants, long tethered flights tend to occur most frequently among pre-reproductive H. convergens females. For all of these reasons we feel justified in assuming that the tendency to make long tethered flights is an indication of willingness to migrate in this species. The relationship between age and flight activity is affected by both photoperiod and food quality. Long flights are not made at all for the first 24-48 hr after emer- gence. After 48 hr post-emergence the tendency to make long flights increases rapidly and peaks from 3-5 days after adult ecdysis. Under short photoperiod and/or poor food quality (frozen aphids) long flights continue for some time in the population. Long day length and high quality food result in a sharp decline in. 0 4 6 8 10 Days at 24°C FIGURE 7. Effect of starvation after (A) 3 days of feeding on live aphids or (B) 7 days of feeding on live aphids on flight activity of H. convergens. Open circles indicate fed animals, closed circles, starved animals. The difference between the flight performances of starved and control animals is significant at the level for A but not significantly different (P = ) for B (Mann Whitney U tes
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
