The Use of Inherited Abnormalities in Studies on the Embryogenesis of Dermestes Maculatus (coleoptera).

THE possibility of using inherited abnormalities in place of conventional experimental embryological methods has been explored by several workers in Drosophila, where there is a large range of lethal and female sterile genes readily available (reviewed Waddington, 1956). These genes are usually pleiotropic, i.e. with manifold effects, and tracing these diverse effects back as far as possible to a single primary defect gives information about the corresponding developmental mechanisms in the normal embryo. Two disadvantages have attended these studies: (1) dipteran embryology is extremely specialized and difficult to relate to that of other insects, (2) it is almost entirely mosaic in character, and therefore throws no light on the important subject of tissue interactions. The present study was undertaken in order to extend this method of embryological analysis to an insect with a less specialized embryology, and hence to show its applicability to studies on insect embryogenesis in general. The beetle Dermestes maculatus was chosen for the following reasons: (1) The embryology of beetles is clear-cut, showing the most characteristic features of insect development in an almost diagrammatic way. (2) The embryology of the Colorado beetle Leptinotarsa, which is similar to that of Dermestes, has been the subject of an extremely thorough experimental study by Haget (1953). (3) The egg of Dermestes is relatively large (approx. 1-0x0-2 mm.), and its chorion is transparent. When put in water on a cavity slide the chief embryological events can be clearly observed by transmitted light under low magnification. (4) Philip (1940) showed that Dermestes is convenient for genetic studies, since its life-cycle is comparatively short (approximately 8 weeks) and each female