Ep. 01 - Goldenrod Galls

Answers to Questions That Arose During the Podcast:


1. Is an inquiline the same thing as a parasite?

Sometimes yes, sometimes no, and, sometimes, we can’t be sure. An inquiline is an animal that lives habitually in the nest or abode of some other species. When an inquiline harms the other species in any way, it is a parasite. If, however, its presence does not have a detrimental effect on the other species, the relationship would be commensalistic (a symbiotic relationship in which one species is benefited while the other is unaffected), not parasitic. At times, this distinction can be difficult to determine; in may instances, it can be hard to say if, and to what degree, an inquiline’s presence is harming the other species.


2. What is the life cycle of the Goldenrod Bunch Gall midge, Rhopalomyia solidaginis?

            During my initial research for this episode, I could find only vague references to the life cycle of the insect responsible for the Goldenrod Bunch Gall. When I finally did track down a source that shed some light, I was left wondering if those other authors left out the details for the sake of simplicity. While the Eurosta fly that makes the Goldenrod Ball Gall has an elegant, year-long life cycle that is easy to wrap your head around, the Rhopalomyia midge leads a life that’s tougher to follow. I had to reread the account several times before it started to make sense. Here’s how it appears to break down:

            The first thing to keep in mind is that the Rhopalomyia midge is bivoltine, which means that it produces two broods in one year, and each brood produces different galls on Goldenrod. Larvae hatch from eggs in the fall and burrow into rhizomes (underground stems), where they overwinter. In the spring, these larvae produce small bunch galls on emerging stems that are difficult to tell apart from stems without galls. This generation pupates in mid-spring. Then, the adults emerge, mate, and lay eggs on more Goldenrod plants.

This second generation creates the larger bunch galls that are seen on Goldenrod starting in mid-June. The larvae live in the base of the gall, within a chamber surrounded by very short and narrow leaves, and those leaves are surrounded by longer and wider leaves. Pupation takes place in early September, and adults emerge in September and early October to mate, lay eggs, and start the process all over again.   

Source: http://www.mapress.com/zootaxa/2009/f/zt02152p035.pdf, pg. 30-31


Work Cited:

Cunan, Ellery T., Thomas HQ Powell, and Arthur E. Weis. "Evidence For Plant-mediated Competition Between Defoliating and Gall-forming Specialists Attacking Solidago altissima." The American Midland Naturalist 173.2 (2015): 208-217.


Hartnett, David C., and Warren G. Abrahamson. "The effects of stem gall insects on life history patterns in Solidago canadensis." Ecology (1979): 910-917.


Mapes, Carol C., and Peter J. Davies. "Cytokinins in the ball gall of Solidago altissima and in the gall forming larvae of Eurosta solidaginis." New Phytologist 151.1 (2001): 203-212.


Eastman, John Andrew. The Book of Field and Roadside: Open-Country Weeds, Trees, and Wildflowers of Eastern North America. Stackpole Books, 2003.


Messina, Frank J. "Plant protection as a consequence of an ant-membracid mutualism: interactions on goldenrod (Solidago sp.)." Ecology (1981): 1433-1440.


Newcomb, Lawrence. "Newcomb’s wildflower guide." Little, Brown, and Company, Boston. xxii (1977).

Peterson, Roger Tory, and Margaret McKenny. A field guide to wildflowers: northeastern and north-central North America. Houghton Mifflin Harcourt, 1996.


Stokes, Donald. “A Guide to Nature in Winter.” Little, Brown and Company, 1976.


Wise, Michael J., Warren G. Abrahamson, and Julia A. Cole. "The role of nodding stems in the goldenrod–gall–fly interaction: A test of the “ducking” hypothesis." American journal of botany 97.3 (2010): 525-529.