Eri Silkmoths Eclose

Our Eri Silkmoths (Samia ricini) have begun to eclose. These were originally obtained from a Europe sourced brood and reared indoors on plum (Prunus). ​They began hatching on 8/22/16 and  spinning cocoons on 9/29/16.

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Today we had four Eri Silkmoths eclose including the pupa from the cut cocoon. Two emerged at nearly the same time around 1:00 PM while the other two eclosed around 6:00 PM. We caught neither of them in the act of escaping the cocoon but it was evident that they squeezed through the trap hole at the top of the cocoons as it was wet and partially dissolved. All four had partially expanded wings by the time we were aware that they had eclosed so we couldn't take any photos of the newly eclosed moth. For the first several hours after the wings expanded, the moths would hold them folded and hang at a 90-180 degree angle, but once they hardened, they relaxed and spread their wings across. disappointingly, the second two males the eclosed has bent and creased wings which is a common problem that samia ricini suffers from due to excessive inbreeding. After inspecting the genitalia, we determined that all four were males which is rather disappointing since we need a pairing, but it's not very surprising since like other Saturniidae, the males tend to have faster growth in the larval and pupal stages and eclose earlier. Thus, hopefully we will get a few females in the next few days before the males become too weak and tattered to mate. 

The moths have primarily greyish brown wings with white patterns and grey margins, and a white body with brown streaks. In addition there is a golden crescent on each fore and hindwing, and a black spot at the tip of each forewing. The wing size for this species is incredibly large in relation to the body size, being around 5 inches across. It's not hard to see how the Atlas Moth (Attacus atlas) which is closely related with similar body proportions can obtain such a large wing span. In addition to the generally large wing to body size ratio, the shape of the wings themselves make them look extremely large, since the tip of the forewings are curved out and elongated and the hindwings are very elongated and pointy in the downward direction. To put things into perspective of how disproportionately large their wing size is, the Samia ricini pupae were mostly under 2.0g while Smerinthus ophthalmica pupae were over 3.0g, but the adult Eri Silkmoth looks at least two times larger than the Ophthalm Sphinx adult.

These moths are truly incredibly beautiful to see in real life, but its just so unfortunate that they had to eclose at this time of year rather than diapausing and eclosing next Spring. Assuming all 14 cocoons will eclose, in order to sustain our breeding stock we will need to rear up another brood which will be extremely difficult during this season since we can hardly find any host plants and the weather is not ideal.

- Alan