A couple of weeks ago, I ended a post by mentioning that I’d just cooked up some milkweed shoots, adding:
…don’t worry, there is plenty left for the monarchs, and the milkweed tussock moths, and the large and small milkweed bugs, and the milkweed long-horned beetles, and the milkweed weevils, and the milkweed leaf-mining flies—all of which are equally deserving of our affection and it drives me nuts when people want to kill or remove any non-monarch organism they find on their milkweed plants. If you simply refrain from mowing your lawn, you will soon have more than enough milkweed to suit everybody’s needs. We got enough from weeding a few strawberry and asparagus patches yesterday to provide the main vegetable for last night’s stir fry and this morning’s omelet, and new shoots keep popping up faster than we can pick them.
I don’t know that anyone read that far besides the two people who commented, which is fine; who has time to read blogs these days? I sure don’t. Anyway, not long after that, I was excited to see one of these lovely creatures in my yard:
A swamp milkweed leaf beetle (Chrysomelidae: Labidomera clivicollis). I encounter these infrequently enough that I forgot to include them in the above list of insects that depend on milkweed.
I bring this up now because last night I was sent two photos of one of these beetles, accompanied by the following note:
Hi, Charley these were on my swamp milkweed mating last week. They are larger than ladybugs. I left them there but a few days later, I noticed the tips of some of the swamp milkweed stems looked stressed and not good. When I unfurled the contracted leaf, I found one of these inside. They were not around last year. I’m thinking they are not beneficial. Do you know these bugs?
I would love it if we could all stop using the word “beneficial” to describe other organisms—the implication being that anything that we do not deem to be “beneficial” is “detrimental” and must be destroyed. We really need to stop thinking that way, and recognize that we are all part of a complex ecosystem, and we need to start acting accordingly. Sure, there are a few insects that compete directly with us for food, and then there are the 99.99% that do not. If the former are causing us problems, it is a sign that we need to diversify our diets and modify our agricultural practices. But this exchange was not about an agricultural pest, so I won’t elaborate on that just now. Here is how I replied:
This is, believe it or not, called a swamp milkweed leaf beetle. Not sure what you mean by “beneficial”; they are less damaging to milkweed than monarchs are, and aren’t related to the stressed stems you observed.
She hadn’t mentioned monarchs, but I knew from past experience that that’s what this was about. (In case our anonymous correspondent is reading this, this is not directed at you personally; I encounter this constantly, which is why I previously wrote the paragraph that I’ve copied and pasted at the top of this post. Our exchange simply suggested to me that I need to lay out my thoughts on this subject more clearly, rather than alluding to them at the bottom of a long post… or in terse, passive-aggressive replies to innocent email inquiries.)
Her response this morning:
Thank you- I think of ladybugs as beneficial because they eat aphids and non desireable bugs. I will look up the swamp milkweed leaf beatle and decide whether to drown , Again this morning it is within the damaged stalk and no other parts of the plant look stressed at all.I just took a photo and will send. Thanks for prompt ID!
These beetles don’t do anything but nibble leaves of milkweed. There is certainly no reason to drown them.
After reading comments on this beetle in Dave’s Garden, I am calling it a non-beneficial pest which would desecrate my plant and deprive the monarchs from the plant I provided for them. Last year I had as many as 12 monarch caterpillars at one time! I eradicated the oleander aphids when I first saw them last year and now will attempt the same with these beetles, treating them the same treatment I give japanese beetles-drowning in soapy water. Thank you again, ______
With this reply, she sent the photo, and I concede that the beetle may well have caused the wilting by nibbling the stem in a way that girdled it. And some of the accounts at Dave’s Garden do sound pretty damning. But it’s hard to judge without seeing the plants in context—I would bet that these tales of woe involve trying to grow small numbers of plants in habitat that is suboptimal for them, making them less resilient than they would be in their natural habitat. I have spent many years surveying wetlands where swamp milkweed occurs naturally, and I’ve never witnessed these beetles causing anything like the devastation these people are describing.
And in any case, it’s a swamp milkweed leaf beetle; doesn’t it have a right to do whatever it needs to do to a swamp milkweed plant? How is it that with the thousands of insect-hostplant relationships out there, so many people care only about milkweed and just one of the insects that depend on it? I love monarchs, don’t get me wrong, but the fixation on this one species at the expense of so many others is causing real harm—including to monarchs. (A couple of years ago I bought a sheet of “Protect Pollinators” postage stamps, and when I looked at them I discovered that the five images they depicted comprised three different photos of monarchs and two of European honey bees. Way to showcase the diversity of our native pollinators, guys.)
How about instead of asking “is it a good bug or a bad bug?” every time we encounter an unfamiliar species, we try asking ourselves: “Am I beneficial?” Of course, this is just as silly a question as asking whether an insect is beneficial (if you click on the above link you’ll see how a much maligned insect creates a valuable resource for numerous other species… and by the way, that magnolia bush is still flourishing). Every action we take will benefit some beings (human and nonhuman) at the expense of others. So we should carefully consider our actions. How is it beneficial to attempt to annihilate every creature that happens to feed on the same plant as this one species of butterfly? Or to entirely ignore the needs of the tens of thousands of other insect species with which we share this continent?
I have put zero effort into attending to the well-being of my local monarchs. I simply let the milkweed do its thing, and eat the shoots that pop up where I’m trying to grow something else. Here’s one patch of the former lawn right next to my driveway, as it looks today:
I saw the first monarch come fluttering through this patch a few days ago. I was happy to see it, and yet somehow the thought of destroying other living things to make way for its offspring never crossed my mind. I did, however, fill a colander with clusters of flower buds to cook up for lunch shortly before taking this photo. Plenty of milkweed for everyone.
Now then, before I was compelled to go on this rant, I was in the process of cataloging all the leafminers and sawfly larvae I’m finding in my yard this season. Two groups of insects that, like monarchs, are fascinating and highly host-specific. Unlike monarchs, these are insects that hardly anyone knows anything about, which is why I’m going to the trouble to share what I’m finding with you all.
Leafminer #56: Calycomyza solidaginis (Agromyzidae). This fly is a specialist on goldenrods (Asteraceae: Solidago), as its name implies.
At first glance, the mine is similar to that of Nemorimyza posticata (see yesterday’s post), but it lacks the herringbone pattern of “toothmarks” and has a relatively clean, whitish appearance due to the larva saving up most of its frass until it’s ready to pupate. And the puparium is formed inside the mine (instead of outside, as in N. posticata), glued to the floor by a big lump of frass.
I wrote about this species once before, and showed a close-up of the curved exit slit in the upper surface of the mine. As you’ll see in the last paragraph there, I didn’t realize at the time that the larva makes that exit slit before pupating, so that the adult will have a way to get out.
Leafminer #57: Phytomyza agromyzina (Agromyzidae). This fly forms entirely linear mines in dogwoods; in this case, gray-stemmed / red-panicled dogwood (Cornaceae: Cornus racemosa). I found a single example yesterday on a small plant that recently sprung up in the area we optimistically refer to as the “nut orchard,” although to date it has yielded us a total of one hazelnut.
In the meantime, in the wild spaces between the young hazelnut, chestnut, butternut, and walnut trees and shrubs we’ve planted, the birds have been doing their own planting, so while we wait for our first big nut harvest, there are pokeweed shoots, tender sumac branchlets (which we used as a sushi ingredient yesterday), wild strawberries, red currants, elderberries, raspberries, and blackberries for us to eat, and dogwood leaves for Phytomyza agromyzina to eat.
Speaking of hazelnuts, I noticed yesterday that a leaf-rolling weevil (Attelabidae) had done its thing on one of the hazelnut leaves:
A week or so ago I found one of these on one of the Chinese chestnuts. I had never seen weevil rolls on either plant before; I most often see them on oaks, and I wrote about sumac and alder leaf-rolling weevils here. I suspect the species responsible in this case is Attelabus bipustulatus, which is the one I’ve seen on oak before and the one I saw working on cutting an alder leaf to roll when I visited the local beaver pond the day before yesterday:
And speaking of blackberries (Rosaceae: Rubus allegheniensis), I noticed yesterday that one of the old dead canes is currently serving as a nest site for a small carpenter bee (Apidae: Ceratina)—you can just barely see its shiny butt in the photo below.
If you want to help pollinators, don’t buy a fancy bee hotel; just stop tidying up your yard! Small carpenter bees will nest in any old, broken, pithy stem, and when they’re done, all sorts of other things will move into their abandoned tunnels, like this adorable yellow-faced bee (Colletidae: Hylaeus) I saw peeking out of one of our cultivated raspberry canes last fall:
And speaking of wild strawberry (Rosaceae: Fragaria virginiana), yet another leaf-mining fly was just getting started on this leaf yesterday:
Leafminer #58: Agromyza idaeiana (Agromyzidae). At least I think it’s this one, as opposed to one of the other two Agromyza species that have been reported from strawberry in North America, neither of which I have ever reared. This was the very first leafminer I ever found in our yard: I collected a few mines just like this one on cinquefoil (Rosaceae: Potentilla simplex) on May 22, 2013, the day Julia and I first visited the house. We bought the house in July, and four adults emerged between September 10 and 23, after we had moved in.
Leafminer #59: Coleophora cornella (Coleophoridae). When I checked the main patch of gray-stemmed dogwood along the border between the “nut orchard” and our neighbor’s yard, I didn’t find any more Phytomyza agromyzina mines, but I did see this:
The larva was still mining away from its portable case on the underside of the leaf:
And on a neighboring leaf I found where it had abandoned its previous, smaller case and excised its current case from a narrow mine formed along the leaf margin:
I haven’t yet reared an adult of this moth. Maybe this will be the year…
Leafminer #60: Agromyza vockerothi (Agromyzidae). This mine was on another blackberry in the nut orchard. This species was described in 1969 from adults collected in four different Canadian provinces, but it wasn’t until I reared adults from blackberry in Massachusetts (including right near my house) 45 years later, and Owen Lonsdale identified them, that anything was known about its natural history.
Leafminer #61: Microrhopala excavata (Chrysomelidae). And right next to that blackberry, I found this beetle nibbling on a goldenrod leaf:
Nothing has been published about the habits of this species (except, of course, in my leafminer book), but over a few years of observation and rearing I’ve determined that it always lays its eggs singly, at the margin of a leaf and on the lower surface, carefully coating them with excrement. The larva’s leaf mine has a distinctive dark brown spot in the center where the frass is concentrated.
Leafminer #62: Microrhopala vittata (Chrysomelidae). In contrast, the leaf mines I found on a goldenrod just 20 feet away had evenly distributed frass, with eggs laid in masses (still covered with poop) deposited away from the leaf margins:
These characteristics identify the maker of the mine as M. vittata—which goes to show that it’s not a good idea to assume that adult leaf-mining insects found in association with mines are necessarily the species responsible for those mines. Microrhopala vittata has been given the common name “Goldenrod Leaf Miner,” a good example of how uninformative and misleading common names can be, given that this is the fifth species of leafminer I’ve found on goldenrod in my yard in the space of a week.
Leafminer #63: Calycomyza novascotiensis (Agromyzidae). Right next to the M. vittata mines were a couple of mines of this fly on hawkweed (Asteraceae: Hieracium praealtum).
As with Agromyza vockerothi, this species was described from Canada in 1969 and nothing was known of its habits until very recently. The first reared specimen came from a mine on H. praealtum that Julia found while weeding a strawberry bed (within 50 feet of the mines shown above) on the exceptionally early date of March 24, 2016. This adult emerged exactly a month later:
That was the last new leafminer I found yesterday, but on my way out of the nut orchard I paused to look at a red currant bush (Grossulariaceae: Ribes rubrum), and discovered that sawfly #15 had just hatched out:
In the photo above, there is a series of about a dozen oviposition scars in one of the major leaf veins, and three recently hatched larvae can be seen munching away. The eggs are inserted in those scars, so I don’t entirely understand how the egg remains come to be on the surface of the vein—I guess the larvae sort of drag them out as they hatch. But that doesn’t totally explain it, because on the right side of the photo below, there is a larva still curled up in its eggshell and resting on the surface of the vein.
This is a species I see every year: Pristiphora appendiculata. The larvae eat a lot of the leaves; I eat a lot of the berries; the plants are perfectly fine; everybody’s happy. It’s almost as if plants evolved to withstand herbivory and don’t need us meddling in their affairs as much as we think.
At the end of a long day—during which I actually did a lot of yardwork in between documenting all those leafminers—I lay down in the patch of milkweed shown at the beginning of this post and Julia joined me. She spotted this gorgeous moth:
I have no idea what it is beyond being in the family Tortricidae, which are known as the “leafroller moths,” but that doesn’t necessarily mean the larva of this species is a leafroller. And then I spotted something I never would have seen had I not been lying on the ground, looking up at the underside of a goldenrod leaf: sawfly #16.
That little cutie in the upper right corner is responsible for those two little holes nibbled in the leaf, which is interesting because very few North American sawflies have been associated with the aster family. As with all the unknown sawfly larvae I’m finding, I’ll do my best to rear it to an adult so we can find out what it is.