Tachinid Flies and Monarch Butterflies

Tachinid flies are small flies that look like hairy houseflies. There are something like 1300 varieties in North America apparently. They are generally considered to be beneficial in that they help control garden and horticultural pests. If you were an organic gardener you would welcome these flies to your farm or yard.

Of course, those of us who like to play God and favor one species over another are on the flip-side of the coin and consider tachinid flies mortal enemies because they prey on our precious monarch caterpillars!

Depending on the variety of tachinid fly, they either lay their eggs on the back of the head of the caterpillar or inject the eggs into the caterpillar. In the case of those eggs that are laid on the the outside of the caterpillar, the larvae burrow into the caterpillar once they emerge. So no matter what, the larvae end up inside the caterpillar enjoying the ride while feasting on our precious ones.

The larvae do not actually kill the caterpillar as they need to allow it to pupate (form a chrysalis) from which the tachinid fly larvae will emerge on mucous-like threads that reach to the ground. "3-2-1 Bungee!" (If you've even been or seen bungee-jumpers you'll get that last reference). Once the fly larvae hit the dirt, they themselves pupate before emerging as flies.

Photo by Nigel Jones at Flickr
Used under Creative Commons License

Well I kind-of sort-of figured I have tachinid flies in my garden. For a start they are nectar-eating flies and I have nectar plants for my monarchs. And I have seen flies that look like this in the photo by Nigel Jones often enough.

Well this morning I was checking some chrysalises that I have sequestered in individual jars so I can test them for O.E. for the Monarch Health research project being conducted by the University of Georgia, and I came across one of the jars with the tell-tale strings hanging down off the chrysalis. Lifting the lid I saw two larvae wiggling on the bottom of the jar.

Of course I grabbed my trusty cell phone and recorded the following video of the action for all to "enjoy". Alien III!

Monarch Butterfly Mating Frenzy

Apparently female monarchs are often reluctant mates which means the male will very often divebomb her and knock her to the ground. He has two hooks at the end of his abdomen that are used to secure the female in his grip; that's if he is successful in doing so as the female will often extend her abdomen vertically making it difficult for the male to attach himself - it is estimated only 30% of mating attempts are successful. Males and females both mate more than once.

When a male secures himself to a female other males in the area may exploit the situation and pile on as can be seen in this animated image made from several photos I took the other day. There were 4 monarchs in on this action. That poor female!

Monarch butterfly mating frenzy
Let's see how many more we can pile on here.

Wasp Eating Monarch Caterpillar - Video

Here’s a video I shot recently of a paper wasp eating a monarch caterpillar that it caught on one of my milkweed plants.


These wasps are the main predator of the monarch caterpillar in my garden here in Orange County, California. Last year it seemed that these wasps captured 100% of the caterpillars, but this year they haven’t seemed to be able to keep up with the numbers, at least to this point. In the last few days all my milkweed plants have been completely stripped bare by large numbers of caterpillars, most of them in their 5^th instar (final stage of their growth as a caterpillar). I had caterpillars wandering all over the place in search of food over the weekend. I relocated some of them to plants that had a few leaves remaining to even out the numbers on the plants, but many of them are now resorting to eating the actual stalks of the milkweed plants. So in a way this year I guess I’m a little bit happy to have the wasps taking some of the caterpillars.

An interesting thing about the wasps is that they do not seem to bother the caterpillars in their 5^th instar. I’m not sure if that really is the case, but I was observing a wasp yesterday that was repeatedly patrolling a milkweed plant that had two 5^th instar caterpillars on it, and despite actually brushing against the caterpillars on a few occasions, it never attacked them. I wondered if they were too big for its eyes to see, or a 5th instar caterpillar is too loaded with carotenoids that the wasp leaves them alone. Have you been able to observe similar behavior in your garden?

So now I am left with bare plants and the cycle goes back to square one. The plants will recover over the next couple of months, proving that they indeed deserve to be called “weeds”. I will cut the stems back a bit to encourage regrowth from the base of the stems. Meanwhile, in a couple of weeks dozens upon dozens of monarch butterflies will emerge from my garden and will hopefully find some milkweed to feed on and lay eggs on in someone else’s garden. Let’s hope we aren't all in this same predicament at the same time.

By the way, if you have landed here on my blog in the same manner that a butterfly lands in your garden – by chance – in addition to this blog I also have my Crazy Monarch Guy Facebook page, and The Crazy Monarch Guy’s YouTube channel where you can see similar videos to this one that I’ve taken of various aspects of the monarch butterfly life cycle and action captured in my butterfly garden. I would love it if you would consider liking my Facebook page and subscribing to my YouTube channel – well, that’s if you are crazy enough, I guess.

Summer Breeze - Monarch on tall verbena

I wanted to post this animated gif of a monarch on a sunflower directly to The Crazy Monarch Guy on Facebook, but unfortunately, even though you can post a gif image file to Facebook, FB does not support animated gifs. A workaround is to post the animated gif here on my website, and then link to it from Facebook. Quite a roundabout way of getting it done, but hopefully it works and you'll get to enjoy this animation of a monarch on some tall verbena blowing in the summer breeze.

Monarch on tall verbena

Monarch butterfly parasites

I have a problem, Houston! 

Dead monarch butterfly pupae - cause unknown

Recently I have had an entire cohort of chrysalises die. I don't know the cause of their demise, but perhaps it was tachinid flies, but at no time did I observe the larvae emerging on their sticky bungee cords. This is what the dead chrysalises look like. I found another three after taking this picture. Such a shame! 100% of the pupae have died. I posted the photos to Monarch Health's Facebook page and asked if they had any thoughts, to which they replied: "It could be one of a variety of pathogens/parasitoids, possibly Nosema bacteria, nuclear polyhedrosis virus, or parasitoid flies (tachinids) or wasps (chalcids)".

In this previous post, I wrote about predators that feed on monarch larvae and butterflies, specifically paper wasps and praying mantises. Today I bring to you the horrors of parasites and pathogens that use our favorite invertebrate as an unwilling host on which to feed, especially in the larval (caterpillar) and pupal (chrysalis) stage of its life-cycle.

Chalcid wasps and tachinid flies both lay eggs on or inject eggs into the monarch caterpillar. Once the eggs hatch, the larvae feed on the insides of the caterpillar. Tachinid flies time their own life cycle so that they pupate within the chrysalis and make their way through the chrysalis wall and drop to the ground from sticky threads. All sounds very yuky, doesn't it! 

Tachinid flies are typically identified by their red eyes. Here are some images of them from Flickr and Google. I actually saw one this morning on one of the milkweed plants near three caterpillars! And here are some images for chalcid wasps from Flickr and Google. Recognize any of these monsters from your own garden?

  

In the reading about parasites and pathogens that I have been doing today I have seen research that indicates that the greater and more concentrated the milkweed and caterpillar population, the greater the level of predation and concentration of parasites. I currently have a lot of milkweed plants in pots close together and I have also been bringing final-stage caterpillars from the milkweed at the front of the house to the back of the house to avoid them wandering into the street when they head off to pupate. From the density of milkweed and caterpillars there are plenty of signals to predators and parasites that host larvae are present. Perhaps I just made an easy target for the wasps or flies that might have parasitized the caterpillars, or if one had an infection, by placing them all on the same plant, the infection was spread. A bit like putting the guy with TB in the middle of a crowd of healthy people! I am learning more and more that it is best not to meddle. 

Asilidae (Robber fly or Assassin Bug)

I also caught this picture of a "robber fly" or "assassin bug" (Asilidae family) in the garden recently. These flies have a deadly proboscis that lances the caterpillar and injects fluids that immobilize the caterpillar and liquefies its insides for ingestion. More yuck! Aren't you glad you're at the top of the food chain?

Robber flies  (Asilidae) are very bristly. Their legs have long, sharp spines to hold onto the prey. Their faces have a dense coat of bristles, called the mystax, presumably to protect them from the legs and mandibles of struggling prey.

Check out more images of "Asilidae" at Flickr. 

I currently have another large batch of 5th instar caterpillars that are about to pupate. Let's hope that this will not be a repeat of the prior batch and that they will all emerge as healthy and beautiful butterflies.

Here's a good article on monarch butterfly predators and parasites from The Monarch Program: http://www.monarchprogram.org/common-monarch-predators-and-pathogens/. 

Asclepias Curassavica (Neotropical Milkweed) - Pros and Cons

Yellow-flowered Asclepias curassavica

Here are some pictures of Asclepias curassavica (common names "tropical milkweed" or “neo-tropical milkweed”). This plant is very popular currently in the US and is the milkweed variety I see most often in stores here in Southern California. The monarchs certainly love it.

There are a couple of varieties: one has yellow flowers, and the other has yellow and red flowers. The plant originates from the tropical parts of the Americas, extending from tropical Mexico in the north to the tropical north of South America.

Red and Yellow-flowered Asclepias curassavica

Unlike many native milkweed varieties found in the United States which are deciduous (go dormant in the winter), "tropical milkweed" grows and flowers year-round. Because of this I actually had caterpillars right through this past winter here in Southern California, and yes, they made it safely to "butterflydom" since in the winter predators like wasps and praying mantises are dormant. The same thing happens in Florida where tropical milkweed is becoming established/invasive.

Asclepias curassavica seeds

There is a debate going on in “monarch butterfly land” as to the dangers of tropical milkweed becoming popular in the range of the eastern monarch migration. This is the migration followed by monarchs that winter over in northern Mexico and which then migrate north following a route east of the Rockies as far as Canada. It has been observed that because of the availability of tropical milkweed in the migration range that some butterflies are choosing to not migrate back south to Mexico in the fall.

Should we care about that or not? There are a couple of arguments put forward against asclepias curassavica. They are, first, that if monarchs do not migrate to Mexico for the winter, there is greater risk of them being killed by a winter freeze in the southern United States. Second, the parasite Ophryocystis elektroscirrha (OE) that debilitates monarchs can survive through the winter on tropical milkweed. Most milkweed varieties native to the United States die down completely to the ground during the winter which deprives OE of an environment on which to survive the winter.

I’m not sure what your take on this debate is. The first milkweed plants I bought were asclepias curassavica. This past winter I bought seeds for a couple of native California milkweeds and have managed to get a few of them established. Perhaps over time I will eliminate the tropical milkweed, but I certainly acknowledge the impulse within me to keep tropical milkweed in my lineup since that means I will have the joy of seeing caterpillars and butterflies through the winter. I am after all, “The Crazy Monarch Guy”, right? Where I live near the California coast frost is about a 1 in 10 years event so most years it would be fine, right? But shouldn't I be encouraging them to fly back to Pacific Grove or Santa Cruz and the other wintering locations along the central and northern coast of California where they will be safer? As always, we love to play god with nature, something that has brought our planet to a very sorry state. Which reminds me to ask, have you read “The 6^th Extinction” by Elizabeth Kolbert? I'm reading it at the moment. Both fascinating and scary. I thoroughly recommend it to you.

Raising Monarch Caterpillars Indoors

I received a message today from someone asking about the pros and cons of raising monarch caterpillars indoors. Her husband built her a really nice netted enclosure in which to grow milkweed outside, but she feels that despite the netting, predators are still taking her caterpillars.

I raised indoors about 150 - 200 caterpillars to butterflies last year so I can definitely give you the pros and cons. In a nutshell there is one of each:

Pro: More monarch caterpillars will make it through the full life cycle and grace the skies with their beauty and lift our spirits to the heavens.

Con: It's a lot of work and a lot of time! Cleaning your enclosure daily, providing a constant supply of milkweed, and coming up with a solution to the problem of where to let the caterpillars pupate will become a daily obligation and burden for you. Having done it for one season, I've retired from caterpillar farming and this year am leaving it to nature to sort it out. So far it's not been too bad and about 50 butterflies have made it.

The one big factor I know that is behind you even thinking of bringing your caterpillars inside is that left to their own devices outdoors, most of them are going to become food for something. This despite all you will read about how the milk in the milkweed is toxic and distasteful and acts as a natural defence against predators. Perhaps that was true before exotic predators were introduced such as the Asian paper wasp, but these days, it's definitely a war zone out there for our beloved monarch caterpillars. The chief predators from my experience are Asian paper wasps. They are on constant patrol from about late May here in Southern California and will pick up many of your caterpillars, especially in their early instars (growth stages). I have also seen praying mantis eating caterpillars of any size as well as the butterflies - they even know to lie in wait by the flowers for the butterflies to come.

So if this is your first year at attempting to help out with the monarch butterfly population, then I know from my own experience that it is very disappointing to finally get butterflies visiting your yard and laying eggs, only to see none of them reach maturity and "butterflyhood". So go for it if you want, but you must make a commitment of time daily to tend your caterpillar zoo.

Here's how I ran my personal zoo last year.

I purchased this small lidded acrylic aquarium from Amazon. I placed a paper towel on the bottom and then three small vases filled with water and milkweed inside the tank. Daily I changed the paper towel, topped up the milkweed.

Once the caterpillars entered the 5th instar (the final stage of the caterpillar stage before pupating into a chrysalis) I would remove the caterpillars and put them into individual glass jars with a piece of cardboard for a lid. I secured the lids to the jars with a piece of scotch tape. (For any 5th instar caterpillars that I bring in from outside currently I just use a piece of paper towel secured across the top with a rubber band). I would drop a couple of milkweed leaves into the jars while the caterpillar was still eating and growing - maybe 2 or 3 days. I would shake out the friss (that's caterpillar poop to most people) before dropping fresh leaves into the jars.

Once the caterpillars were ready to pupate, they would climb to the top of the jar and pupate hanging from the cardboard lid. At some point before the butterfly emerged (10 to 14 days), I would hang the lid inside one of these picnic food tents I also got from Amazon where they would eclose (hatch/emerge) and I would release them at the end of the day when I got home from work.

Here are a couple of things I learned later that would have saved me some time, well actually, a lot of time. First, you don't need to make air holes in the cardboard lids; I spent hours punching four holes in each lid! The caterpillars are never going to use up all the oxygen in the jar, nor is the makeshift lid likely to be airtight. Second, I spent a lot of time stringing up the lids in the food tent. Now if ever I am going to move a chrysalis I detach it and hang it from string. Here's a basic rundown on how to do that:

Tie a piece of 0.5mm nylon cord (something like this at Amazon) around the stem of the chrysalis using a non-slip knot (I use a "reef knot" that I remember from my days as a boy scout - left over right and under, right over left and under). Once you have secured the knot around the black stem gently pull down dislodging the fine cobwebby mesh that the caterpillar makes to hang his black stem from. Then I just tie the chrysalis to a twig in a tree out of the sun - chrysalises do not do well in full sun.

So that's my brief rundown on my method of raising monarch caterpillars indoors. Let me know in the comments if you have any questions and I'll try and answer them if I can. Perhaps you have your own technique or ideas you would like to share too. Please do. As they say, there's more than one way to skin a "cat".

Happy monarch caterpillar farming!

Monarch Butterfly Research Tagging Projects

Tagged Monarch Butterfly Cal Poly Monarch Alert Project

This tagged monarch butterfly showed up in my garden last year. It had traveled 18 miles / 29km from its place of release.

There are several research programs devoted to the monarch butterfly, and if you are crazy for monarchs then you might like to become a tagger too to help out with this research.

Don't panic, you don't have to tag every butterfly that emerges to take part; just tag the ones you can.

 When I reported this butterfly I got an email from Jean, the woman who had tagged and released it. She is an avidly crazy-for-monarchs person like me who gardens for butterflies in Rancho Santa Margarita here in Orange County, California. I went over and visited her and her garden and helped her tag some butterflies. It was great to know that us crazy-for-monarch people are not alone in this world.

 Here are two links if you wish to get involved in tagging monarch butterflies that emerge from your butterfly garden.

East Coast population: http://www.monarchwatch.org/tagmig/tag.htm 
West Coast population: http://monarchalert.calpoly.edu/

Have a crazy day!