Nature Miramichi:

From: David McLeod <mcleodda@nbnet.nb.ca>
Sent: Thursday, July 2, 2020 10:17 PM
Subject: Re: Nature Miramichi – Hybrid Cecropia X Columbia

As a rule different species of moths do not hybridize, as the chemical composition of the pheromones produced by the female to attract a male for mating usually only attract a male of the same species. So hybrids are not a common occurrence naturally.

However, a few studies using reared specimens of Hyalophora cecropia and H. columbia, the Cecropia and Columbia silk moths, have shown that male Columbia moths will mate with female Cecropia moths. I’ve also come across a few reports of natural hybridization in the state of Wisconsin, Ontario, P.E.I. and Nova Scotia, all places where the normal range of both species overlap. The Cecropia larvae are known to feed on the foliage of a wide variety of deciduous trees and shrubs, while those of Columbia larvae feed only on the needles of Tamarack or Larch (Larix laricina) (sometimes erroneously called Juniper in the Miramichi area).

In the journal, Northeastern Naturalist, Vol. 13, No. 1, 2006, there is an article entitled: A Case of Natural Hybridization Between Hyalophora cecropia and Hyalophora columbia (Lepidoptera: Saturniidae) in Nova Scotia (Bridgehouse). The following information paraphrases parts of this article:

In June, 2002, the author captured a gravid (with fertilized eggs) female Cecropia at a black (ultraviolet) light, from which he reared larvae that had some protrusions (tubercles) arising from the back of each segment that were differently coloured from the typical Cecropia larvae – the first hint that hybridization might have occurred. After pupation, twelve cocoons were kept in cold storage until May of the following year (2003) from which they were then removed to room temperature. Both male and female adult individuals emerged in June, which had the hybrid wing colouration similar to the one in Lisa’s photos. However, as it turned out, only the males of this cross were sexually viable, while the females were sterile. Judging by the wide, plumose (feathery) antennae of the individual in Lisa’s photos, it is a male, so it has the possibility of mating with a female of either species this year. I’ve never heard what the resulting generation of such a union would look like, but presumably it could be done artificially in a laboratory setting.

Another interesting fact, determined by research on the two species, is that female Cecropias “call” by emitting an airborne pheromone (which can be detected by males up to a distance of one kilometer) at or near sunset. On the other hand, female Columbias release their pheromones just once shortly before sunrise, continuing after dawn until about 6 AM. It has also been found that “virgin” female Cecropias, those who have not successfully mated at their usual time between sunset and midnight, will stop calling about midnight and resume again just before dawn when female Columbias are also calling, thus making it more likely to attract a male Columbia mate, resulting in the production of a hybrid generation.

Fascinating stuff!

Dave