Monday, May 13, 2019

Citheronia splendens...Splendid Royal Moth

If you think a name like Splendid Royal Moth is a little too over the top for a moth, I'm here to change your mind! They are a truly spectacular moth: large, mouse gray with red-orange stripes and pale cream splashes. Their caterpillars don't quite reach the 6 inches their eastern cousin, the Regal or Royal Walnut Moth Citheronia regalis, does (in fact, that larva is so eye-catching it has its own colloquial name: Hickory Horned Devil), but C. splendens larvae are beautiful in their own right, having many rich colors and patterns as they develop into 4-5 inch lavender beauties with black and orange spikes.

Citheronia (sith-er-oh-nee-ah) splendens primarily occurs in Mexico but enters the southern edge of Arizona and far SW corner of New Mexico. Larvae feed on wild cotton (Gossypium thurberi) and pointleaf manzanita (Arctostaphylos pungens) with some records on evergreen sumac (Rhus virens choriophylla) and skunkbush sumac (Rhus trilobata), both native to the area.

I reared two C. splendens in 2017 from eggs. It was an amazing experience and I took hundreds of photos but never finished editing and making a selection of them to share until now.

Because I didn't have access to any of their native host plants, I first tried tempting them with ornamental cherry/plum and black walnut, since C. splendens is reported to accept black walnut in captivity and their cousin C. regalis is known to frequently feed on black walnut and occasionally plum species in captivity, plus these were my only freely available options that were anything close to what they might eat. These are the leaves you'll see in the first few photos. The larvae nibbled on both a tiny bit but refused to accept either.

Larval instars are noted as L1 (first instar), L2, L3, L4 and L5.
Remember that you can click on a photo to view in full-screen, and use the arrow keys to flip through all the photos in this post that way.

Eggs at 10 days old, head (black spot) becoming visible, August 8, 2017
Eggs at 11 days old, most of larva is visible (lots of scales from the mother were stuck to the eggs), August 9
Newly-hatched L1 larvae, August 10
Newly-hatched L1 larva, they are about 1/4 inch long at this stage, August 10
Newly-hatched L1 larvae, August 10

Once it became apparent that they didn't like these host options (granted, the black walnut wasn't in the best shape but I couldn't reach any fresher leaves, and I had my doubts about the ornamental cherry anyway) I went to plan B and tracked down some staghorn sumac (Rhus typhina) which is native to northeast US, to test if they'd eat it. Bingo! They hungrily chowed down immediately. So I bought one at a nursery, set it up on my apartment's porch and rigged a sleeve of sorts: one of my rearing cages has a hole with a sleeve on the side, which I slid over a branch of the bush, tied it off and then hung the cage from a plant stand to keep the weight from pulling down on the branch too much.

Late L1 in common resting position for this stage, August 14
L1 preparing to molt, August 15
New L2, August 16
Staghorn sumac (Rhus typhina) with my rearing cage setup

The molt to third instar gives a hint of what's to come, with lavender-tinted dark gray and more extensive orange markings.

Mid-L3, about an inch long or slightly bigger, August 22
Mid-L3, August 22
Late L3, about 1.5 inches long, August 26

Around this time, I started noticing that one larva was growing faster than the other, so I started calling the bigger one 'Larva A' and the smaller one 'Larva B'. The following images will note which larva by the letter, as you'll start to see the difference in dates and which stage each is in at the time.
Also note that the longest spines are solid white immediately after the molt to fourth instar, but within a couple hours the tips turn black and the head and legs darken with more orange and black.

Larva 'A' a few hours after molting to L4, August 28
Larva 'B' immediately after molting to L4, also note the brown patch with cluster of eyes, August 30
Larva 'B', new L4 with molted skin, August 30
Larva 'A', mid-L4, August 30
Larva 'A', mid-L4, August 30
Larva 'A', mid-L4, August 30

By this stage, L4, the larvae are about 3 inches long and have started to reach out and pull each leaflet to themselves and munch down one side of the rib and then the other, often consuming much of the rib by the end of the process.

Larva 'B', mid-L4, September 4
'A', late L4, September 4

By late fourth instar, larva 'A' was a lighter gray-lavender color while larva 'B' was slightly darker with a rosy tint. This difference continued into the fifth (final) instar as you'll see later.

'B', late L4, September 7

Final instar! I have to admit that while the larvae were a hefty 3 inches at this stage, I was a bit disappointed that they weren't bigger as they entered the fifth and final instar, thinking that perhaps I had stunted them by not being able to feed them their native hosts. What I didn't know was that they would spend over two weeks in this stage and add over an inch to their length!

'B', newly molted into L5, September 9
'B', newly molted into L5, note the little cluster of eyes on the head, September 9

'A', early L5, September 5
'A', L5, September 6
'A', L5..."I'm not moving if I don't have to, just gotta stretch a little more to reach it!", September 7
'A', L5, September 7
'A', L5, September 7
'A', L5, September 10

They were so heavy at this point that it was difficult to get a photo of the dorsal (back), because if I rotated a stem around they would slide over to one side or the other or simply droop upside down. It was around this time that I started carting them around with me to various places to show people these incredible creatures. The reactions were fun to see! As one person put it when seeing 'A' stretching across my palm and slowly crawling up my arm, "that's not a caterpillar, that's a SNAKE!"

Around September 10, they had grown so big that I couldn't stuff enough branches into the small rearing cage to keep them fed for more than a couple days and I was concerned they might contract a bacterial or viral disease from the cramped conditions. Considering there were only two caterpillars and they were so big that I couldn't easily lose them, I decided to lay out a small tarp in my living room, put the sumac bush on it and simply let them have at it with no containment. I delighted in those final two weeks of "hanging out with my caterpillars in my living room", cherishing every moment since I knew I may never have an opportunity again to rear this species. It's one thing to have a bunch of caterpillars on cuttings in a large rearing cage in my living room (which happens often), but quite another to have two giants free on a large bush where I can watch them eat from across the room.

'A', mid-L5 at 4.5 inches, only about a quarter inch more to go before she pupated, September 14
'B', early/mid-L5 at 3.4 inches, September 16

You can really see the color difference between 'A' and 'B' now. Although they kept eating for another week, they only gained about a quarter inch after this point, mostly putting on weight in preparation for pupating.

'A', mid/late L5 at nearly 5 inches, September 16
'B', mid-L5, note the rosy hue, September 18
'A', late L5, note the pale brownish lavender compared to 'B' above, September 18

Larva 'A' stopped eating and started crawling around looking for a good place to pupate on September 21. Larva 'B' started this activity on September 27.

'A', prepupal "walkabout stage", September 21
'B', prepupal stage, September 27

C. splendens does not spin cocoons but instead the larvae burrow about six inches underground and pupate in a chamber they hollow out in the soil. In order that I could watch the process and maintain a clean environment for the pupae, I ripped up a bunch of paper towels and stuffed them into a half gallon glass canning jar and placed the larva inside. I learned from experience years ago that soil-pupating caterpillars will chew threw mesh cages even if you have it stuffed full of paper towels for them! It took about seven days for the caterpillar to find a spot to her liking, discharge excess fluid and shrink down before finally pupating. Because she settled next to the glass, I was able to watch the process, she even used the fluid to kind of mush the paper towels into a big cavern. However, the glass jar made it difficult to get any pictures so I just waiting until she was all done and then carefully pulled out the new pupa as you see below.

'A', newly-formed pupa, September 28
'A', newly-formed pupa, September 28
'B' newly-formed pupa and shed caterpillar skin, October 5
'A' (top) and 'B' (bottom), hardened pupae on October 27, ready for overwintering.

'A' emerged on July 15, 2018, a gorgeous female! When disturbed she would flash her wings up like this.
'A' on July 15, 2018, natural resting pose
'A' on July 15, 2018

'A' on July 15, 2018, closeup of her head and legs.

For comparison, here is a male Regal Moth, Citheronia regalis, which emerged in 2011 from a pupa I purchased.

Regal or Royal Walnut Moth Citheronia regalis for comparison.

In case you are wondering what happened to 'B', these moths can be difficult to properly trigger into emerging and she never did last year. However, the pupa is still flexible and has some weight, so appears to still be alive. I overwintered her again and will try to imitate natural cues again to see if I can get her to emerge. They need to be sprayed with water starting in June and exposed to very warm temperatures to imitate the monsoon rains and summer heat of southern Arizona. Many species of butterflies and moths are known to stay dormant as pupae for multiple years until the conditions are "just right".
Because these moths are not native to Washington, of course I can't release them but they will live on in my specimen collection and be used to teach people about these spectacular moths.

I hope you enjoyed this photographic journey!

Update: moth 'B' emerged on July 8, 2019, another gorgeous female. Very exciting to have complete success on a rearing project, even if I did have to wait two years!