The embryonic development of Diprion pini and the related ecdysteroid levels

The embryonic development of pine sawfly Diprion pini (L.) was studied in relation to ecdysteroid levels by histological analysis with light microscopy and immunoenzymatic assay. The progressive differentiation of cells, tissues and organs, including the hypocerebral ganglion, the corpora cardiaca, the corpora allata and the prothoracic glands, was described. Only two germ layers, i.e. the ectoderm and the mesendoderm, were detected. It was also highlighted and defined the deposition of three embryonic cuticles, of which the first secreted by the serosa and the other two by the ectoderm and epidermis, respectively. The deposition of the first and of the last cuticle occurred after a peak of ecdysteroid secretion.