Cynthia Silkmoth & Jacobs' Silkmoth Cocoons Arrive

Our cynthia silkmoth (Samia cynthia advena) and Jacobs' silkmoth (Rothschildia jacobaeae) cocoons have arrived. 

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Today we had six cynthia and four Jacobs' silkmoth cocoons arrive. They are freshly spun but we do not know if they are diapausing, though we will know in the next few weeks based on if they eclose or not. Regardless of when they do, we plan to obtain pairings and eggs from them.

Above are the cocoons of the cynthia silkmoth (Samia cynthia advena). The Samia genus is taxonimically ambiguous, but these should be the subspecies advena, which refers to the population in eastern North America that was introduced from China in the late 1800s in attempt to start a silk industry. They are very closely related to the eri silkmoth (Samia ricini) that we have and are currently rearing which is also a species used in the silk industry.

The cocoons are somewhat irregularly shaped, being generally narrow and tapered at both ends, though more so at the top. Three are still wrapped in the leaf of some plant. They are slightly narrower and more compact than our old eri Silkmoth cocoons as seen in the comparison in the bottom two photos. As for color, the cynthia cocoons are a light tan while the eri's are almost white. In grams, they weigh 1.5, 1.7, 1.8, 1.9, 2.7, and 2.8 respectively, which averages to 2.07 each. However, the masses are clearly bimodal, with heavier suggesting female and lighter suggesting male, meaning we likely have two females and four males. 

The general life history of the S. c. adevena is probably extremely similar to that of S. ricini, and will therefore also be extremely easy to rear. The caterpillars utilize ailanthus (Ailanthus altissima) in the wild but will take a variety of alternatives in captivity such as Prunus and Ligustrum which we will use if the moths eclose next spring. However, if they are not diapausing and we must rear the caterpillars this winter, we might have to experiment with citrus (Citrus) which we are currently feeding our ricinis. We look forward to seeing the differences between each life stage of S. c. advena and S. ricini. 

And here (above) are the Jacobs' silkmoth (Rothschildia jacobaeae) cocoons. This species is endemic to Argentina and is part of the very diverse Latin American genus Rothschildia (Rothchild's silkmoths). The genus is said to be the New World relative of the Asiatic genus Attacus based on adult morphology (they look quite similar, being primarily brown with large transparent portions on each wing), though this could be symplesiomorphic so their taxonomic relationship is still debated.

The cocoons are shaped somewhat like those of Hyalophora cecropia but are much smoother and less tapered at the top. They are a light brown and quite thin, caving in easily when pressed. It does not look like there were ever leaves attached to them due to the very perfectly smooth surface, though there are indentations on the ventral sides where the twigs were removed. In grams, they weigh 2.5, 2.8, 3.6, and 3.8 respectively which averages to 3.18 each. However, just like the cynthia cocoons, the masses are bimodal, with heavier suggesting female and lighter suggesting male, meaning we likely have two females and two males. 

​We have not yet raised a Rothschildia species yet (though we have unsuccessfully attempted to rear the allied Eupackardia calleta once), so we really don't know much about them let alone any specific characteristics of this particular species. For example, we aren't even sure what hosts plants R. jacobaeae utilizes in captivity. Though fortunately, the caterpillars (like most Attacini silkmoth larvae) should be able to use various plants in the Oleeae tribe (family: Oleaceae) such as ashes (Fraxinus sp.), privets (Ligustrum sp.),  common lilac (Syringus vulgare), and possibly others. If any of these fail, we can try other typical Rothschildia or Attacini hosts if they are available, such as Prunus and possibly Citrus. In the case that these cocoons are not diapausing and we have to rear them this winter, then we plan to use glossy privet (Ligustrum lucidum), the only local species of privet we have, or citrus. Until then, we have both these and the cynthia cocoons placed in a plastic box lined with paper towels and lightly misted. 

- Alan