Subject: moth identification help
Location: Benicia, California
April 10, 2014 10:18 pm
My kids and I love bugs. We found an egg sac in our yard that we have not seen before. We have been keeping an eye on it for a about a month (although I don’t know for sure how long it had been there before we found it). It hatched this morning and we found a beautiful moth (which we also have not seen before). I’m hoping you can give us some more info about what kind of moth it is exactly. Thanks so much.
Signature: Christie

Tiger Moth

Tiger Moth:  Grammia ornata

Hi Christie,
This is a beautiful moth.  It is a Tiger Moth in the subfamily Arctiinae, and it looks like a member of the genus
Grammia, however we are having difficulty finding a visual match on BugGuide because of the black base on the underwings and the intricate pattern on the forewings. We also find the cocoon to be unusual in that no caterpillar hairs have been incorporated in its construction.  We have decided to contact our friend and Arctiid expert Julian Donahue for his opinion.

Tiger Moth

Tiger Moth:  Grammia ornata

Hi again Christie,
We emailed Julian and then telephoned, but he is running errands.  We now believe this is
Grammia ornata, and you can see a selection of images on BugGuide including this image on BugGuide which shows the black base to the underwings.  The species is found in California.  We are awaiting confirmation from Julian.  We could not locate an online image of the cocoon of Grammia ornata for comparison. 


Unidentified “Cocoon”

Julian Donahue Confirms Identification:  Grammia ornata
You’re right on, Daniel. Grammia ornata is a western North America species, occuring from Ventura Co., California north through the Pacific Northwest to southern British Columbia, Canada, east to northern Utah, and western Wyoming and Montana. (South of Ventura Co., California, it is replaced by the similar G. hewletti, described from San Diego Co., California).
Attached is a copy of Chris Schmidt’s revision of Grammia, which has color plates illustrating all the species. Both species are illustrated on p. 578, figs. 36 & 37.  Schmidt_2009_Grammia

Thank you so much for your reply. I was wondering about the cocoon/egg sac as well. It looked like thousands of tiny oval eggs inside a silk web, but in the shape of a caterpillar. This one was on our deck under a planter, but we found two more on the underside of leaves  on a  nearby plant with the web curling the leaf around it. We have not seen any actual caterpillars in the garden, so now I’m wondering the sac and the moth were coincidental occurrences?? I would love to know more about the cocoon/sac if possible.
Thanks again!

Hi Christie,
In your original email, you implied that you were certain the moth emerged from the cocoon.  Now you don’t seem certain.  In our opinion, the moth and the cocoon are not related. 

Julian Donahue confirms our suspicions about the “Cocoon”
The “cocoon” doesn’t look like anything I’ve ever seen; almost 100% positive it’s not arctiid in origin (sorta looks like a sawfly larva to me, but that’s a wild guess and I have nothing to back it up).


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Location: Benicia, California

2 Responses to Tiger Moth is Grammia ornata with unknown “cocoon”

  1. Christie says:

    I think the egg sac/cocoon in my photo was actually parasitic wasps that had over taken the caterpillar as it was spinning its cocoon.

  2. Kerry C says:

    i wish that cocoon egg sac thingy was identified as I have just found that exact thing on a geranium leaf in my “Happy Hut” (my greenhouse -the infamous & no longer made “Thinking Outdoors” greenhouse which looks like a large shed made by Rubbermaid-, which is more of a grow room due to our using various lighting sources for both light & heat as we live in New Jersey, but I totally digress….) & came upon this site doing a Google image search. Another site had found something similar & let the eggs hatch & they turned out to be tiny wasps! YIKES!!! Kill it w/ fire; NOW! Soooo not a fan of wasps as I was once stung over 75x & spent a week in the hospital. I don’t know what a sawfly looks like so I’ll have to do some searching to see what they are. I do have an adult female & a young male Praying Mantis in my Happy Hut. The male was living on the plants I have in a large urn from my garden that I keep thriving until next Spring & I caught the female hanging out on the vinyl siding of our house on Halloween evening & brought her in to keep warm. She rewarded my kindness by laying an egg sac last Tuesday , 3 November, 2015. Besides them I know there are the menagerie of usual suspects from pill bugs & aphids, house & blue bottle flies, little golden moths & ants, the occasional carpenter bee & yellow jacket wasps find their way in too so the mantises can feed on them instead of each other but I don’t know where this wormy looking cocoon thingy chock full o’ teeny tiny eggs came from! I now see that someone else commented before me about the possibility of wasps & I’m not going to douse the thing with alcohol & set it on fire to ensure death!!! I’m sure wasps (& spiders too) serve some sort of good purpose but having dealt w/ those horrid things & enduring hellacious agony from their stings & venom; I’ll not risk it. Maybe I’ll first offer it to the mantises (if I can find either of them) to see if they’ll eat it but no matter what; I’m not going to allow the eggs to hatch. Yeccccccch!

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