More Obsessing about Coyote Brush

Posted November 8th, 2010 by John Callender

A running joke in my family these days is that I have a crush on coyote brush. We were playing “20 Questions” at the dinner table a few nights ago (anything to get William beyond grunting), and when it was my turn to choose and I announced, “vegetable,” William got it in one, asking with a roll of his eyes, “Is it coyote brush?”

Sigh. I can’t help it. That plant is just so cool.

I previously wrote about the infestation by what I believe was orange tortrix (Argyrotaenia franciscana) along the trail below the Sidenberg Overlook at the bluffs. The infestation was really bad for a while, but the plants have bounced back. Coyote brush has co-evolved with A. franciscana over a very long span of time; apparently the occasional infestation is no big deal. The same plants that basically had no healthy-looking foliage at all two months ago now look like this:

We’re reaching the end of the flowering season for coyote brush, and some of the female plants look like they’re covered in snow. Here’s a closeup of some seeds getting ready to set sail:

When you start paying attention to coyote brush, you can’t help but notice the great variety of insects that associate with it. Here are some photos I’ve taken lately.

Bob Carlson, a retired entomologist who previously did postdoctoral work studying Ichneumonidae, was nice enough to comment on these images I uploaded to Bugguide. He thinks the bluish tint to this small wasp’s eyes suggest that it might be a male (because it lacks the female’s long ovipositor) of the Agathidinae subfamily:

Here’s another wasp, this one crawling around on a Rhopalomyia californica bud gall. It’s not a great photo, but I’m wondering if this might be a species of Torymus, a group of parasitoid wasps that prey on the larvae of gall midges.

No luck so far on an ID for this fly, but after I posted its image at Bugguide and asked for any ideas about what was going on with that bubble of liquid coming from the fly’s mouth, I got a pointer to this interesting discussion: tiny bubbles.

According to my copy of Russo’s Field Guide to Plant Galls of California and Other Western States:

Coyote brush (B. pilularis), also called chaparral broom, is one of the most interesting shrubs entomologically. Tilden’s monumental study (1951) of this shrub identified over 221 species of insects associated with it, as well as eight species of mites. The insects, in turn, hosted an additional 62 species of parasites for a total of 291 species on coyote brush…

As mentioned earlier, the intricacies of host plants, gall inducers, parasites, and inquiline relationships, especially as exemplified by the coyote brush regime, are vastly complicated and a worthy subject for additional study in the future.

You hear that, scoffers? “A worthy subject”!

The Tilden referred to in that passage is James Wilson “Bill” Tilden, who passed away in 1988. He did his 1948 doctoral dissertation at Stanford on the insect associates of B. pilularis. The dissertation was 408 pages long, according to this obituary published in the Journal of the Lepidoptrists’ Society: James Wilson Tilden (1904-1988): A Remembrance (PDF file). I’d love to get a copy of that dissertation.

Not quite as long, but still very much a current object of my desire, is the “monumental study” Russo refers to, Tilden’s 1951 paper, “The Insect Associates of Baccharis pilularis De Candolle”. It was published in Microentomology, a journal that hasn’t yet made it onto the Web, unfortunately. The paper is 39 pages long, and according to a reference I was able to google up, they have a copy at the UCLA Biomedical Library. I think I’m going to have to pay a lunchtime visit to Westwood during one of the days when I’m working in Santa Monica.

7 Responses to “More Obsessing about Coyote Brush”

  1. Sara says:

    Just came across your blog while trying to figure out why academic paper searches for Ichneumonidae and Baccharis weren’t turning anything up, despite hearing rumors from entomologists that associations between these groups exist. Curious whether you tracked down the 1951 Tilden paper and if it contained much in the way of Ichneumonidae.

  2. John Callender says:

    I did track it down eventually, and yes, Tilden does mention a number of Ichneumonidae that he found in association with B. pilularis. Here’s the list he gives in the paper (with the caveat that this is 1951-era taxonomy; I’m not sure what changes might have occurred since then):

    Camploplegidea species, near bellula (Dalle Torre)
    Cryptohelcostizus alamedensis (Ashmead)
    Diplazon laetatorius (Fabricius)
    Horogenes eureka (Ashmead)
    Horogenes pterophorae (Ashmead)
    Iseropus, new species
    Mesochorus, new species
    Mesochorus species
    Phoeogenes, new species, near vincibilis Cresson
    Pimplopterus species
    Scambus aplopappi, (Ashmead)
    Scambus pterophori, (Ashmead)

  3. Kat says:

    Just ran across this blog when looking for an answer to what’s going on when I see the coyote brush this time of year have globs of what looks like spit at their tips. Is this a secretion, or an effect of an insect, or what? What purpose does it serve? Thanks!

  4. John Callender says:

    My guess would be that it’s the spittle mass created by a spittle bug, or “froghopper”. Here are some links:

    This is an image I took in April of last year at Lake Los Carneros in Goleta. It shows a coyote brush plant with a bunch of “spittle masses” on it:

    Here are some more pages with information about spittle bugs:

  5. Kat says:


  6. Eric Brennan says:

    Hi John
    It’s good to see others that are enthusiastic about Coyote Brush. I’d love go get a pdf copy of the Tilden paper (Tilden, J.W. 1951, The insect associates of Baccharis pilularis De Candolle. MICROENTOMOLOGY 16(1):49-185) if you have one. My email is

    Below is a link to a video that might interest you. I made it a few years back and it starts off with a conversation between me, playing a role of an air traffic controller, and a hover fly coming into land on a coyote brush plant in a hedge row at the USDA organic research farm in Salinas.
    Brennan E.B. 2015. A biological control buffet in the salad bowl of America.

    Thanks, Eric

  7. Caroline Ayres says:

    Thanks for this interesting post. I too am obsessed with coyote brush. I find it intriguing that it seems to come in so many sizes and shapes. As well I’ve been observing the many many bugs on my coyote brush plants and it’s been really interesting!

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