Wednesday, May 22, 2019

Rearing butterflies and moths

With the rearing projects I've done over the years, I've never written out everything I do or problems I've learned from. The following instructions are based on my personal experiences rearing various species, mostly in the Saturniidae family (giant silk moths). These notes are aimed towards the casual rearer, someone who may have found a caterpillar or wishes to raise a few eggs through to adults.

Large-scale rearing operations require established host plants in order to support numbers of caterpillars in the fifties or hundreds. In order to contain the larvae and protect them from predation and parasitism, people usually place large mesh sleeves over branches that are tied off at both ends, or occasionally they may have large walk-in mesh cages with potted bushes.

My rearing operation is what is considered a small-scale operation, with less than 40 larvae of any one species, mostly fed with cuttings of their host plants. If the plants are small and something I can buy at a nursery, like kinnickinnick or other forbs, I'll keep the whole plants in my rearing cages, which are in three sizes: 12" cubes, 14x14x24" and 24x24x36".

Eggs
Place a paper towel in the bottom of a plastic or glass container (I often cut to fit) and then place the eggs on the towel. Keep the lid of the container on, opening it once every day or two when you check the eggs. Keep in mind these critters are tiny and need relatively little oxygen, so you won't suffocate them in an airtight container. My preferred container size is a square plastic Rubbermaid sandwich container, although I've used a variety of containers, including small glass canning jars.

In some species, eggs change color or develop a pattern a day or two before the larvae hatch. Sometimes you can even see the caterpillar through the eggshell within 24 hours of them hatching. Eggs of some species overwinter (these are usually laid in the fall), but eggs of most species will hatch in 7-14 days, with most in my experience hatching around 10 days after being laid.

Rubbermaid sandwich container used for hatching eggs and feeding 1-3 day old larvae

Newly-hatched caterpillars
Within a couple hours of the larvae hatching, place one or two small sprigs (or leaves if it's something big like madrone) of their host plant on the paper towel in the container. If it is an airtight container, the cutting will usually remain fresh for 24-48 hours without any additional moisture. The paper towel helps absorb excess moisture that could lead to fungal growth which can kill the caterpillars.

Reasons I don't put the newly-hatched larvae immediately into a large cage on branches of host plant:
  • If I'm not sure they'll eat a particular host, it gives me the chance to test a few options in small amounts and be able to see if they're eating one or the other.
  • New larvae don't stay on the host plant very well during the first 24-48 hours, they often wander. In the wild, they would typically be on a large plant or tree so would have lots of room to crawl around and still be on the host. If I put them in a large cage right away, they sometimes fall off the cut branches or crawl off one and onto the cage walls, then crawl all over the cage trying to find the food again.
  • The airtight container keeps the food fresh for at least 24 hours without requiring it to be wrapped in a wet paper towel or placed in a vase with water. Larvae are very susceptible to drowning, especially when they're so tiny that it doesn't take much water.
All of the above gives the larvae the best chance at survival. Once they are eating well, they're less likely to wander off of the plant cuttings. This is when you should move them to the main rearing cage. They should not be kept in the airtight hatching container for more than 2-3 days or the humidity may build up too much and cause bacterial or viral infections, or the food can become moldy.

Rearing caterpillars in mesh cages
Rearing cages come in a variety of shapes and sizes. I use the collapsable (aka popup) style with fine mesh on all sides except one side that is made of clear vinyl for easy viewing. These cages allow good air flow while keeping even the tiniest caterpillars contained and also protected from parasites and predators. Small 10-12 inch cube cages are excellent for portability (I always keep one in my truck in case I find something in the woods I want to take home!) and for rearing small batches of larvae. I use medium cages (14x14x24) for most rearing and two large cages (24x24x36) when I have particularly large cut branches and/or caterpillars, like when I reared the Ceanothus Silk Moths on Douglas-fir and Pacific Madrone last year.

Some of these pop-up cages don't sit flat very well because of the curved wire frame. This can be a problem if your plant cuttings are top heavy or in a vase that is easily tipped over. I get around this by using large, flat-bottomed containers such as quart or half gallon canning jars and being careful to place the cage on a hard surface like a table or supported by walls in a corner of my porch or living area. If you or someone you know is handy with wood-working, you might try cutting a piece of plywood to fit the inside of the bottom of your cage to stabilize it. You would need to curve or otherwise blunt and sand the corners to fit properly so the board doesn't wear holes in the mesh.

Place an old towel or layers of paper towels on the bottom of the cage to collect the frass, this way you can easily roll it up and shake it out in the garbage to keep the cage clean. You should do this every few days or at least whenever you change the plant cuttings, to keep the caterpillars' environment clean.

Don't overcrowd the caterpillars, this can lead to viruses or other problems killing them or resulting in otherwise unhealthy larvae.

Keep the cage in a well-ventilated area, outside exposed to the natural temperatures is best if you have a covered space, but I usually keep them inside next to a bright window.

The most critical part of rearing caterpillars is keeping the food fresh.

Live plants
If at all possible, feed your caterpillars on potted plants inside a medium to large rearing cage. Many host plants are available at nurseries, even if they aren't the exact native species your butterfly or moth is used to. There are a few native plant nurseries in the northwest that are also good sources.
Be mindful of how the plants have been grown and cared for. I've read that most plants aren't sprayed at the nursery where you're buying them, only where they were grown, which would wear off by the time you buy them (I bought some plants recently that specifically said they were only grown with biological control methods, like ladybugs to control aphids). However, milkweed plants being sold by some big box stores a couple years ago were discovered to have tags indicating they had been grown with systemic neonicotinoids, a very deadly pesticide to insects that can remain in the plant for months. I don't know if this is still being done, but just be careful to read all the tags on the plants prior to purchase.

Cut plants
In most cases for small-scale rearing, you will be dealing with cut branches. I manage these in two ways. The critical part is ensuring that your caterpillars can't access the water source and drown! This is a common problem, so you are not alone if you lose a couple caterpillars this way, but it is nonetheless devastating.

Method 1: wrap the cut end with soaked paper towels and place in a plastic baggie tied off tightly with a rubberband or twist tie. I do this for small to medium twigs, such as when I'm starting off some young caterpillars or rearing a species that has very small larvae even when they are full grown.

Method 2: use a vase or other container with water, plugging the opening very tightly with paper towels or plastic wrap. This can make it difficult to change out the stems, so I usually do this when I have a lot of caterpillars requiring large branches that take up a lot of water, or if I am using host plants that do very well as cut stems for long periods of time, such as willows or evergreen trees and shrubs. The easiest way to do this is with a narrow-necked vase that you can put 1-3 stems in it and then stuff paper towels around any remaining gaps in the vase to keep the larvae from crawling down the stems and drowning in the water. If you have larger branches and need a bigger container, I like to use quart or half gallon glass canning jars, but these can be more difficult to seal up. If you put so many branches in the jar that it only needs a few gaps closed off, it's not hard to use pieces of paper towel. Sometimes I cover the top of the jar with 2-3 layers of plastic wrap and a rubberband, then pierce the plastic layer with the stems, then seal up any loose gaps or rips with pieces of paper towel.
If you stuff a lot of paper towel into the gaps to the point that it starts absorbing water from the jar, it can open up some of the holes, so keep an eye on that and stuff more paper towels in it.

No matter what, check your caterpillars frequently and watch for any that may slip through a gap you missed. If you find one early enough, you may be able to revive it if you put it on a dry paper towel and very gently blot it.

Plants that do well as cuttings can be kept fresh for up to two weeks. If the cuttings start dropping leaves or become brittle, replace them as soon as possible to keep your caterpillars healthy. Most cuttings can be kept in the refrigerator for a week or two and stay very fresh, just wrap the cut ends in wet paper towels and place the entire cutting into a gallon ziploc bag or even a small trash bag, seal it most of the way, then blow into it to inflate the bag and quickly seal the rest of the way. I've had great success with this method! I'll also keep extra cuttings in a bucket with water to change out the cuttings in the rearing cage through the week for larger projects, such as the Ceanothus Silk Moths I reared on Douglas-fir and Madrone last year.
If you can obtain fresh cuttings more often than once a week, that is of course ideal, but if you can only gather the cuttings on weekends, just make sure to plan ahead and gather a little more than you think you'll need for the week.

Moving the caterpillars
Use a small paintbrush, like a watercolor brush, for moving the larvae to fresh food. Be gentle and slide it under them from the side, kind of rolling it a little and gently pry them off the stem they're on. You may need a larger brush if the larvae are larger than an inch long and have stinging spines. Otherwise with most species, once they're about an inch or bigger, they become easier to move by hand or with a small stick. Sometimes I just clip off the section of stem they are on and prop it on the new cuttings, often they'll immediately start to crawl onto the fresh leaves.
Count your caterpillars! This ensures you've accounted for all of them when you move them to fresh cuttings. They can be easy to miss, so usually I remove the old cuttings and clip off all the leaves or pieces of stems they are attached to and place them in a temporary "holding pen", then once the fresh cuttings are ready, I transfer all the larvae to the new branches.

Preparing for pupation
Once your caterpillars have finished eating they will start crawling around the cage looking for a place to pupate. Butterflies will usually hang from or otherwise attach their chrysalis to stems of the host plant or the inside of the rearing cage. Moth species that spin cocoons will spin up in the branches of the host plant cuttings. When they start doing this, do not replace the cuttings or disturb the caterpillars, keep them in a spot where they won't get jostled around. Once the cocoons are formed, wait at least a week before moving them, to allow time for the pupa to form. If you know the cocoons or butterfly chrysalids will overwinter, you may carefully cut the twigs they are attached to and prepare them for overwintering (I'll save that for another blog post). Otherwise, just dump out the water in the jar but keep the twigs in the cage and wait for the adults to emerge.

If you are rearing a moth species that pupates underground without spinning a cocoon, watch out! Those caterpillars will chew right through your cage and hide in all corners of your house! If you have earth-pupaters (like sphinx moths, a few Saturniids and others), keep a close eye on the larvae as they reach maturity and as soon as they start crawling around the cage for a day without eating, immediately move them into a plastic or glass container filled with crumpled paper towels. A five gallon bucket with a lid works well for this. You can provide them a pot of soil at least 6 inches deep, but you'd need to make sure the soil was free from fungus and potential parasites. It will take a few days for the caterpillar to develop into the pupa, so leave them in a quiet dark place for at least a week. If they are a species that overwinters as the pupa, place them in a container for the winter (I'll discuss this more in a future post on overwintering), otherwise, place the pupae back into your rearing cage to await the adults in a couple weeks.

I'm open to other rearing tips, so please share your experiences!

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!

Sunday, May 12, 2019

Spring in the Columbia River Gorge

Yesterday I visited a few of my favorite spots in the Columbia Gorge to see what was flying and dust off my Nikon camera a bit. Images are from Klickitat Canyon (all the "browns") and Grassy Knoll trail head (greenies).

Propertius Duskywing male, Erynnis propertius

Pacuvius Duskywing male, Erynnis pacuvius

Pacuvius Duskywing male, Erynnis pacuvius, nectaring on chokecherry

Pacuvius Duskywing male, Erynnis pacuvius, nectaring on chokecherry

Brown Elfin, Callophrys augustinus, nectaring on chokecherry

Sheridan's Green Elfin/Hairstreak, Callophrys sheridanii, probable male

Sheridan's Green Elfin/Hairstreak, Callophrys sheridanii, probable male

Sheridan's Green Elfin/Hairstreak, Callophrys sheridanii, probable female

Sheridan's Green Elfin/Hairstreak, Callophrys sheridanii, probable female (same one as above)