Component Communities: Enchanter’s Nightshade

by Carl Strang

 

Today I return to my studies of leaf-eating insects at Maple Grove and Meacham Grove Forest Preserves. In an earlier post I went over my continuing study of the trailing strawberry bush, still recovering from its 1980’s devastation by the ermine moth at Meacham Grove.  Then I reviewed the leaf miners of black/sugar maples, which have been showing a number of interesting patterns in these forests.

 

Now I want to expand the story further by looking at other plants and their consumers I studied in the 1980’s. Today’s focus is the enchanter’s nightshade.

 

Enchanter's nightshade; bird scat mimicking moth resting on leaf

Enchanter's nightshade; bird scat mimicking moth resting on leaf

 

 

 

This plant is a common annual in DuPage County woodlands. It produces arrays of tiny white flowers in mid-summer, then little burs that spread the seeds by sticking to passing animals.

 

Circaea (the genus name refers to Circe, the sorceress of Greek mythology) has a number of consumers. Minute white dots on the leaves are signs that lacebugs or other sucking insects remove the contents of some of the leaves’ cells. Brown areas appear to be caused by a fungus. There is a leaf miner, which I have not identified, and a leaf beetle that I collected but was unable to match to known species. Finally there are two moths: Cerastis tenebrifera, the reddish speckled dart, a member of the huge family Noctuidae, and an inchworm or geometrid moth, Trichodezia albovittata, the white-striped black.

 

The last is interesting in that it is brightly marked and flies in the daytime, so that you might think it a small butterfly.

 

Trichodezia mounted specimen

Trichodezia mounted specimen

 

 

 

The green caterpillars stay on the plant all day, holding their bodies out stiffly when resting so that they mimic their own damage, resembling leaf petioles from which the blades have been chewed away.

 

Trichodezia larva

Trichodezia larva

 

 

 

Cerastis caterpillars feed at night, hiding in the leaf litter during the day. They are the earliest major consumers, active in June, while Trichodezia and the leaf beetle are feeding in July. The leaf beetles fly to the plants at dusk and feed at night. They chew elongate holes between the leaf veins, in contrast to the caterpillars’ chewing in from the edges.

 

There were tantalizing hints of interactions among some of these species in the 1980’s, which have me thinking about going back and looking at this system again. Leaves with brown spots appeared to be avoided by caterpillars and by sucking insects, suggesting that these herbivores were avoiding the fungi or chemical changes induced by them. In a year when Trichodezia were abundant, they and the leaf beetles seemed to be avoiding leaves with one another’s damage.

 

I did not find any of these chewing insects on other plants. This kind of specialization produces little communities centering around each species of plant, leading the ecologist R.B. Root to coin the term “component community.” Collectively these plants and their consumers form a “compound community.” Certainly my observations support this understanding of forests. The component community structure leads to an ecosystem with impressive biodiversity (i.e., variety of living things).

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3 Comments

  1. January 17, 2009 at 1:01 pm

    […] yesterday’s subject, I want to focus on the component community centering around Solomon’s plume, another flowering […]

  2. April 26, 2009 at 11:08 pm

    […] a skipper butterfly, suggested that this was one of our few day-flying moths (I described another, Trichodezia, last winter). A quick check of the references confirmed this late April moth to be a member of the […]

  3. June 4, 2014 at 5:56 am

    […] and I was reminded of my 1980’s investigation of forest moths in DuPage County, for instance the component community centering on enchanter’s nightshade. Perhaps I need to expand a bit, and make a more concerted effort with moths at future […]


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