After patiently waiting for almost a year, the Hyalophora euraylus cocoons I’ve had since last spring have finally begun to emerge. At the end of May last year, all eleven of the remaining H.euryalus caterpillars I had reared, completed the second stage of their development. However, these moths only have one brood per year, so I had to patiently wait almost a full year to see the adults and the result of my hard work to keep the caterpillars alive and well.
This species overwinters, meaning it needs to experience some below average temperatures to complete its life cycle. The moth is found throughout California’s mountain ranges and emergence times vary depending on how long the cold temperatures last. In southern California and along the central coast these moths emerge somewhat early, mostly between February and March. If the winter is very mild and there are only a few weeks of below average temperatures, the adults will emerge as early as mid to late January. Along the northern coast and sierra foothills, the first adults emerge around the end of March to late April and sometimes the beginning of May. At higher elevations (Above 4500-5000ft) adults aren’t on the wing until late May to early July.
Due to this wide range of emergence times, it can be somewhat easy to plan a trip to blacklight for them in a certain area. The only downside when trying to collect the adult moths is that fly very late at night, sometimes as late as 3-4am. So, if you are willing to pull an all-nighter to catch this moth then this species is the right one for you. There are easier methods to finding and rearing this moth however, and they bypass the staying up till dawn method that many silkmoth enthusiasts do. One method is to look for the caterpillars on any of the host plants that they feed on, which can be a hit or miss depending on what part of their range you are in. The other is to look for wild cocoons on the branches of host plants. I have only tried looking for the caterpillars once before but was unsuccessful. I will most likely try to find H.euryalus caterpillars again this year while I search for caterpillars of different moth species that I am also searching for.
Of the adult moths that emerged, one of them was female. In order to not have any inbreeding occurring, I decided to take the newly eclosed female to an area near Auburn where there were reports of H.euryalus on the wing. I had tried a different area the week before but had no luck. So, when I took the female to Auburn, I was in high hopes of drawing in wild males. At around 1am the female began to scent. This is the process where female moths release a pheromone to attract males so that mating can occur.
Unfortunately, no males came to the area where the female was scenting. However, two large female H.euryalus had flown to the blacklight/MV lights that I had set up earlier in the evening. The first flew in around 9pm and the other a little past 11pm. Both of the wild females caught at the light were gravid (full of eggs) and thus I was able to obtain eggs despite my failed attempts with the recently emerged female I had brought with me. The next evening, the gravid female from Auburn laid almost one hundred eggs, making the trip a success. The eggs hatched a little over a week later and the rearing process began again for 2018. I am hoping for a pairing of the adult moths in 2019 from 2018’s caterpillars so that I can continue the lineage for the next couple years. I look forward to rearing this species again this year and I am excited to see how much variation there is between each individual adult moth that has yet to emerge.
I live in Southeastern South Dakota. I received a Horstman’s Recurved Larch from Oregon this spring. In June I found an H euryalis caterpillar on it! It spun a cocoon on June 30. What should I do from this time forward? Will it emerge before our cold weather hits end of Oct-November? Or should I bring it in if it doesn’t?
Hello! That’s awesome you have the cocoon! H.euryalus is univoltine, which means it only has one generation per year. Their cocoons are double layered and are very very hardy. You can leave the cocoon as is outside and it will be fine. It will overwinter as is and can even be under snow. By next May or so the moth will emerge. Keep an eye on it between late April to May to see if you can catch the moth emerging. Hope this helps!