. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HYBRIDIZATION IN BUTTERFLIES 45 The first adult flight was apparently not observed; it is probably very short in duration. The 1942 samples were obtained at monthly intervals rather than semi- monthly as in 1941; therefore, the chance of missing a short adult flight is in- creased. The second and third broods of 1942 are to be found indicated in the figure a few weeks earlier than in the preceding year. As 1942 was a warmer year for Mono Lake than was 1941, an earlier start in larval development in the spring, with a consequ
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HYBRIDIZATION IN BUTTERFLIES 45 The first adult flight was apparently not observed; it is probably very short in duration. The 1942 samples were obtained at monthly intervals rather than semi- monthly as in 1941; therefore, the chance of missing a short adult flight is in- creased. The second and third broods of 1942 are to be found indicated in the figure a few weeks earlier than in the preceding year. As 1942 was a warmer year for Mono Lake than was 1941, an earlier start in larval development in the spring, with a consequent shift forward in the successive broods, would thus be expected. The two 1940 samples at Mono Lake show no yellow butterflies present at all. Therefore, it would appear that they were obtained in a yellow interbrood period (Fig. 1). The frequency at Round Valley does not follow this sequence of events (Fig. 1). Neither the 1941 nor the 1942 samples show any correlation with those % 80 70 60 50 40- 30 20 • \ A , |Q. M0t*0 LAKE ------- l( ' / \'o ROUND VALLEY - \ / \ \' ,'' \ / / \ V" /. o ...... - v — •«..-. APRIL MAY JUNE JULY AUG. SEPT. OCT FIGURE 1. Frequency of yellow to orange butterflies at Mono Lake and Round Valley, California, throughout the season. Note the complete absence of yellow at certain times at Mono Lake as compared with Round Valley. of Mono Lake (Table I). This shows the complete lack of intermixing between the two places though they are only fifty miles apart. The 1941 Round Valley curve is high in late June (60 per cent yellow) and drops to a low in late July (25 per cent yellow). A rise occurs in mid-August (53 per cent), with a subsequent drop again the first of September (34 per cent), and then a last rise in early October (55 per cent). If these fluctuations represent successive broods not completely separated one from the other, then there are many more generations present per year at Round Valley than at Mono Lake. This would be expect
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
