Life on a Bolete

Time for another installment of my celebration of fungus fauna.  The day after Hurricane Irene came through my woods, I went for a walk to survey the damage.  There was practically none, as it turned out, other than the hickory tree next door that fell onto the hemlock in my yard, although there were lots of little broken twigs on the ground, some bearing strange galls I’d never seen before.  As I was walking past this bolete, which was a bit past its prime, a little purple speck moving across its surface caught my eye.

It was the springtail Ptenothrix marmorata, which as shown in my first fungus post is not an unusual thing to find walking around on a mushroom in these woods.

Ptenothrix marmorata (Dicyrtomidae; 1.8 mm).

Ptenothrix marmorata (Dicyrtomidae; 1.8 mm).

From a standing position, this nearly 2-mm bug was the only animal I could see on the bolete, but kneeling down to get a better look at it I saw some smaller specks moving around, all of which turned out to be springtails.  The largest of these were Entomobrya ligata.  I have found this species before by peeling chunks of bark off of dead trees, and its cousins (E. nivalis) by breaking open the black knot fungus galls on cherry twigs.

Entomobrya ligata (Entomobryidae; 1 mm).

Intermingling with these were even smaller springtails in the genus Ceratophysella.  These relatives of snow fleas (Hypogastrura) sometimes form large, purplish masses on puddles in the winter and early spring.

Ceratophysella (Hypogastruridae; 0.8 mm).

These three springtails represent the three major orders of springtails (Collembola, formerly considered an order of class Insecta, is now recognized as a class of its own). Ptenothrix marmorata, along with the garden springtail (Bourletiella hortensis), belongs to Symphypleona, the globular springtails.  Entomobrya ligata represents order Entomobryomorpha, the elongate-bodied springtails.  Ceratophysella and the snow fleas are in Poduromorpha. The remaining order is Neelipleona, which has just 35 described species worldwide. Just one of these is represented on BugGuide.net so far: Megalothorax minimus, which is only a quarter of a millimeter long.  So maybe it was on that bolete and I just missed it.  I did see a similarly small springtail wander across the frame while I was trying to photograph an E. ligata:

Entomobrya ligata (Entomobryidae; 1 mm) and Sminthurinus quadrimaculatus (Katiannidae; 0.3 mm).

Sminthurinus quadrimaculatus is a tiny globular springtail, and I had seen it once before, when one of the mycologists at the Berkshire BioBlitz called me over to see one he had found wandering around on a polypore he was examining under a microscope.  That one was of the two-spotted form, rather than this four-spotted form that gives the species its name.

Sminthurinus quadrimaculatus (Katiannidae; 0.3 mm).

I was unable to find this one again once I’d taken my lens off of it; otherwise I would have tried for some better shots.  There was a slightly tinier thing that was also invisible to me, but which I stumbled upon a couple of times as I scanned the surface of the bolete through my camera’s viewfinder:

A tiny, stalked egg (0.25 mm) found on the surface of the bolete.

I saw the long stalk on this egg and immediately thought of parasitoid wasps.  I remembered reading about some chalcidoid wasps having stalked eggs, but hadn’t bothered to include this information in my book since I didn’t imagine anyone would ever come across one.  I have since learned that certain ichneumons also have stalked eggs. Since the last wasp I’d seen on a mushroom was a eucoiline figitid, I wondered if they, too, might have stalked eggs.  A quick Google search got me to a paper* about eggs of cynipoid wasps, and sure enough, they do.  (However, see my next post for more thoughts about this egg.)  The hosts of eucoiline figitids include vinegar flies (Drosophilidae) whose larvae develop in fungi, and while I was sitting by this bolete, it was visited by some of the little orange vinegar flies that seem to be on most of the fermenting mushrooms around here.

Vinegar fly (Drosophilidae; ~2.5 mm).

Just before I got up to continue on my walk, another fly alighted on the bolete–a fungus gnat, which was smaller than I realized fungus gnats could be.  Unlike the vinegar flies, it was willing to hold still for a picture (for the photo above, I had to cheat and use a shot of a vinegar fly found on another fermenting bolete later in the week).

A tiny dark-winged fungus gnat (Sciaridae; ~1 mm).

* VÅRDAL, H., G. SAHLÉN and F. RONQUIST. 2003. Morphology and evolution of the cynipoid egg (Hymenoptera). Zoological Journal of the Linnean Society 139:247–260.