Voracious Little Ladies

Here's a nice find from this afternoon:

Coleomegilla maculata, Van Patten Woods FP,
Lake Co, IL 5/14/14

This is Coleomegilla maculata, one of approximately 500 species of lady beetle found in the US. It's a native species, and has played an important role in biological control of aphids in various agricultural settings.

That role is fading, though, because of these two:

Seven-spotted Lady Beetle (Coccinella septempunctatus),
Illinois Beach SP, Lake Co, IL 9/16/2012

This one is the Seven-spotted Lady Beetle (Coccinella septempunctatus), from Europe.

Asian Multicolored Lady Beetle (Harmonia axyridis),
Illinois Beach SP, Lake Co, IL 10/29/2011

And this one is the Asian Multicolored Lady Beetle (Harmonia axyridis), from Japan.

Both of these species were intentionally introduced to the US to try to control aphid pests. (1, 2) While they do appear to be effective in that role, their novelty has allowed first the Seven-spotted and then the Asian to become the dominant members of the family in most locations across the country. After introductions in the late 1980's, the Asian species reached Canada in the early 1990's. (3)

Their spread across the continent has coincided with declines in many of our native species. (2, 4) Although some authors are cautious about the causes of these declines, others have tested the Asian beetles for competition with native ones, finding that the new guests are most likely responsible for much of the decline in two native species: Cycloneda sanguinea in Florida (5) and the species I started this post with, Coleomegilla maculata, in Kentucky. (6)

Most of our conservation efforts (and dollars) go to the big, charismatic vertebrates. But conservation of little arthropods can be just as important. Here we have a passel of native species apparently being driven to scarcity by a couple of invaders that we didn't simply allow in, we invited them. Frankly, if Lady Beetles in general weren't such useful critters, we probably wouldn't have even noticed. Which has to make you wonder what other critters are slowly vanishing beneath our notice.


(1) Tedders, W. L., & Schaefer, P. W. (1994). Release and establishment of Harmonia axyridis (Coleoptera: Coccinellidae) in the southeastern United States. Entomological News, 105(4), 228-243.

(2) Brown, M. W., & Miller, S. S. (1998). Coccinellidae (Coleoptera) in apple orchards of eastern West Virginia and the impact of invasion by Harmonia axyridis. Entomological News, 109(2), 143-151.

(3) Coderre, D., Lucas, É., & Gagné, I. (1995). The occurrence of Harmonia axyridis (Pallas)(Coleoptera: Coccinellidae) in Canada. The Canadian Entomologist, 127(04), 609-611.

(4) Colunga-Garcia, M., & Gage, S. H. (1998). Arrival, establishment, and habitat use of the multicolored Asian lady beetle (Coleoptera: Coccinellidae) in a Michigan landscape. Environmental Entomology, 27(6), 1574-1580.

(5) Michaud, J. P. (2002). Invasion of the Florida citrus ecosystem by Harmonia axyridis (Coleoptera: Coccinellidae) and asymmetric competition with a native species, Cycloneda sanguinea. Environmental Entomology, 31(5), 827-835.

(6) Cottrell, T. E., & Yeargan, K. V. (1998). Intraguild predation between an introduced lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae), and a native lady beetle, Coleomegilla maculata (Coleoptera: Coccinellidae). Journal of the Kansas Entomological Society, 159-163.