Chorion morphology of the Eri-silkworm, Samia cynthia ricini (Donovan) (Lepidoptera : Saturniidae)

The Samia cynthia ricini chorion was observed for its surface and inner str uctures by scanning electron microscopy. A micropyle opening was present at the anterior pole region of the chorion surface, surrounded by 12 to 20 pe tal-shaped cell imprints forming a single rosette. There were 6 to 10 "sper m ducts," dangling from the inside surface of the chorion at the anterior p ole region; these were connected to the micropyle and probably facilitated the polyspermy. All surface areas were confirmed to have network patterns m ade of comparatively uniform polygonal imprints. Aeropyles opened at the ju nction of three polygonal units, and there was an additional large hollow a t the intermediate region of each polygonal unit. Cross-sections of the cho rion revealed three layers, the outer, middle and inner layers. The middle layer, which was the thickest, was further divided into the upper, intermed iate and lower parts; the aeropyles and the additional hollow penetrated al most to the intermediate part. The intermediate part was characterized by i rregular lamellae, which were porous and thus may facilitate gas changes.