30. Observations on the Life‐History, Biology, and Genetics of the Lady‐bird Beetle, Adalia bipunctata (Mulsant)

Abstract

1 Adalia bipunctata has so many varieties that it is highly suitable for the needed study of inheritance of normally occurring variations. 2 Adalia can be mated in captivity with ease, but their cannibalistic habit makes it very difficult to rear them satisfactorily in large numbers. 3 The time passed in the various stages is variable, depending not only on the food, hut also on the temperature, to which all stages, but especially the pupal, make a rapid response. 4 Little is known of either hibernation or migration, but apparently both septempunctata and bipunctata tend to collect in numbers in the spring and autumn, and may at times be found hibernating, piled upon one another, similar to the “masses” of Hippodamia found in the western U.S.A. 5 There is no evidence of dominance in crosses between the two main forms–the Red “type” and the Black (var. 4-maculata and var. 6-pustulata). 6 Eleven ma tings of Red produced only the Red type. 7 Black and Red forms also occur in G. variabilis, and, as in bipunctata, neither is dominant. 8 The pronotum of the Black form is darker than that of the Red, but there is no progressive blackening of the pronotum of the Red coincidentally with the increase in the size of the black spots of the elytra. 9 Although it is possible to make a series from pure red elytra on the one hand through various patterns to pure black on the other, this cannot be regarded as proof that the variations are merely fluctuating. The percentages of the variations is, as far as is known, approximately stable, and certain types are far more common than others. These facts, combined with the observation that the children tend to show the variations of the parents, strongly suggest that there are probably certain points of genetic stability, and that only analysis is needed to show that there is some regular method of inheritance.