Friday, March 27, 2020

Species Profile: Hera Buckmoth - Hemileuca hera

Hera Buckmoth or Hera Sheepmoth (Hemileuca hera) is a large, black and white, day-flying moth found in sagebrush-steppe habitat across the western United States. In our area, it occurs in eastern Oregon and Washington. See my earlier post on Hemileuca species in the Pacific Northwest for other details about its life history. Hera is notoriously difficult to rear and there are few published descriptions. While out looking for butterflies (unsuccessfully, due to the cool, overcast weather), a little black clump on some sagebrush caught the corner of my eye. Closer inspection revealed them to be first instar Hera larvae! Super excited, I clipped off the branch and carried them home to rear, ignoring the fact they feed exclusively on sagebrush in desert habitat and I live on the west side of the Cascades, far from sagebrush. Thus my adventure began!

Sagebrush-steppe habitat in eastern Kittitas County, WA where I found Hemileuca hera larvae on April 20, 2019.
Hera Buckmoth (Hemileuca hera) - late 1st instar larvae on basin sagebrush (Artemisia tridentata) in Kittitas County.

A day after I found the larvae, they began molting into the second instar. The light brown larvae on the right (below) just molted. The lighter gray larvae on the top left and bottom left molted earlier, while the dark black larvae are about to molt.

Hera Buckmoth (Hemileuca hera) - larvae molting into 2nd instar on April 21, 2019.

Hera Buckmoth (Hemileuca hera) - 2nd instar larva.

During the first week, I fed the larvae on cut basin sagebrush (Artemisia tridentata) in a small cage (below). I kept the ends wrapped in wet paper towels placed in plastic baggies and secured around the top with twist ties and binder clips. The cuttings stayed surprisingly fresh for at least five days before starting to yellow.

Hera Buckmoth (Hemileuca hera) - my rearing setup for the first week.

Hera Buckmoth (Hemileuca hera) - 2nd instar larvae.
Second and third instar larvae were solid black with black bristles and silvery hairs. They moved and fed together in such tight bundles that it was impossible for me to accurately count how many there were. Because of this, I am uncertain how many might have died, although I was very careful to clean the cage and examine the leaves and branches when replacing food and I never noticed any dead larvae. My attempts at counting the larvae in the 3rd and 4th instars always resulted in 20-21. One died in 5th instar and I ended with 18 pupae, so the true total was probably 20 and I must have lost a larva in the 3rd or 4th instar.

Hera Buckmoth (Hemileuca hera) - 3rd instar larva.

After the first week with cuttings, I fed the larvae on potted Artemisia tridentata for two weeks. Unfortunately, the sagebrush didn't do well and started to yellow so I was back to obtaining fresh cuttings the following two weeks. I loaded up my hungry caterpillars for a 600 mile round trip drive (I'm a very dedicated caterpillar momma!). I found some lush sagebrush growing on the side of a road pullout before the mouth of the Deschutes River in the Columbia Gorge. It had big, long leaves compared to most of the surrounding sage, which I didn't think much of at the moment, figured it just had more moisture or something. I loaded up a bag full of cuttings and headed home. A colleague commented that the leaves looked different in my pictures and after studying information on different sagebrush species, I tentatively identified it as Artemisia cana, silver sagebrush. Hera seem to exclusively use A. tridentata throughout their range, only one larva has ever been found on A. cana in the wild, so I was a bit nervous that I might be damaging my chances of successfully rearing these picky cats, but they voraciously took to the fresh cuttings and continued feeding well on it for the next two weeks until I was able to purchase several pots of A. tridentata I then switched them back to.

Hera Buckmoth (Hemileuca hera) - 3rd and 4th instar larvae on Artemisia cana.

Fourth instar larvae exhibited orange-yellow bristles on the two dorsal (back) rows and white spiracles. In all of my rearings of Hemileuca eglanterina, larvae of that species look similar to hera at this stage, except that eglanterina has these orange bristles on all spines dorsally and laterally through most instars.

Aren't they cute? But don't touch! As with all other Hemileuca species, the caterpillars have urticating (stinging) hairs that feel like running your hand through a stinging nettle patch. You might get away with allowing the larvae to crawl on your hand without being stung, just don't try to pick them up or touch their backs!

Hera Buckmoth (Hemileuca hera) - 4th instar larva on Artemisia cana.
Hera Buckmoth (Hemileuca hera) - 4th instar larva on Artemisia cana.

Hera really are quite beautiful in the fifth (final) instar! They have variable markings in pale yellow and pinkish cream on their bodies, white spiracles (breathing holes), non-stinging silvery hairs on their body, long black spines with either black or yellow branches tipped with silver stinging hairs.

Hera Buckmoth (Hemileuca hera) - closeup of 5th instar larva.
Up to this point, the larvae developed steadily, molting into the next instar every 12-13 days.

Hera Buckmoth (Hemileuca hera) - 5th instar larvae on Artemisia tridentata.
At this point, the larvae had been in the 5th instar for two weeks. I was expecting them to prepare for pupation any day, and they did spend half their time crawling around the cage, but they acted more like they were looking for food, in spite of there being plenty, and as soon as I picked them up (with a paintbrush!) and put back on the plants, they always went back to eating. This became a daily routine, every morning and evening, to carefully transfer the larvae from the bottom of the cage back onto the plants. This is likely the time when larvae in the wild are spreading out to feed singly instead of in large groups. I had enough potted plants to keep 1-2 larvae per plant, but the plants were only 10-12 inch tall plants from a native plant nursery. Plenty of leaves for them to eat, but possibly not enough space for this apparently super picky stage of their development.

Hera Buckmoth (Hemileuca hera) - 5th instar larvae on Artemisia tridentata plugs placed in a PVC pipe and masking
 tape grid to try to keep them spaced apart. However, this made it difficult for the larvae to find
 the plants again after dropping off.

Hera Buckmoth (Hemileuca hera) - 5th instar larva on Artemisia tridentata.

Unless the larvae are out feeding near the ends of the branches, it would be easy to overlook these larvae if you didn't have a really good search image as they blend into the silvery glint and broken shadows of the sagebrush.

Hera Buckmoth (Hemileuca hera) - 5th instar larva on Artemisia tridentata; it is surprisingly well-camouflaged!

Hera Buckmoth (Hemileuca hera) - 5th instar larva on Artemisia tridentata.
At this point (weeks 8-10), the potted sagebrush was half eaten so I placed all the plugs into a box (figured this would also provide a nice dark place for pupating) and also provided more A. tridentata cuttings. Although the larvae continued to drop off the plants and crawl all over the cage, this setup made it easier for them to find the leaves again without me putting them back on the plants.

Hera Buckmoth (Hemileuca hera) - rearing cage with potted and cut sagebrush,
set outside for sun exposure, temperatures between 85-92F and good ventilation.

You may have noticed at this point that I kept the larvae inside or outside at different points. I experimented with different conditions because Hera are used to being fully exposed to sun and wind. Living on the west side, outdoor conditions in April-May are cloudy and in the mid-60s at best, with higher humidity than sagebrush-steppe habitat. Keeping the larvae outside gave them 1-2 hours of sun per day and a bit of fresh air, but was higher humidity (60-80% RH) and cooler than I thought they appreciated. Keeping them inside gave them a steady 70-73 degrees 24 hours a day and lower humidity (35-40% RH) but only provided what little sunlight could reach through my windows. After a couple weeks, I had an idea to set up my full-spectrum plant light and purchased a UVA-UVB bulb rated for desert reptiles. I figured that if reptiles need that spectrum to keep them healthy, my caterpillars would probably benefit as well. Here is what my setup looked like, with adjustable height of the lamps depending on what cages I was using.

Hera Buckmoth (Hemileuca hera) - rearing cage setup indoors with full-spectrum plant light
and a UVA/UVB bulb rated for desert reptiles in an attempt to replicate sun exposure.

FINALLY!!! After over a month (37+ days to be exact!) of dilly-dallying, the larvae finally started showing definite signs of preparing to pupate...

Hera Buckmoth (Hemileuca hera) - prepupal larva.

Over the years, I've played around with different items for ground-pupating moths. In this case, I was concerned that keeping the larvae in a closed container like a bucket or gallon jar might not be ventilated enough for this desert species. Also, I was about to head out on a two week road trip and didn't want to leave them in a mesh cage that could easily be disturbed with jostling around and moving luggage. I pulled out my blancher - perfect! Lots of holes for ventilation but just small enough the larvae couldn't fit through them, it's dark so mimics being underground, and it is small enough that I could fill it with several ripped-up and crumpled paper towels without using up a whole roll. I could hear them rustling around in it for a few days and then it was all quiet.

Hera Buckmoth (Hemileuca hera) - prepupal larvae.

Around 8-10 days later, I opened the blancher and carefully searched through the paper towels to find all the pupae...18 total!

Hera Buckmoth (Hemileuca hera) - prepupal larvae and pupae.

Back home from my trip, I tucked all the pupae between folds of a cotton towel placed in a cage kept on my porch to be overwintered. One of them had other ideas though: this gorgeous female emerged on September 22, 2019, much to my surprise! If nothing else emerges this coming summer, I will still feel like I was successful to at least get one of these fussy beauties all the way through to adulthood.

Hera Buckmoth (Hemileuca hera) - adult female.

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