Accuracy of lady beetle ID by volunteers

Over the past two years I have been surveying lady beetle abundance across the state of Ohio with the help of 250+ volunteer citizen scientists. These volunteers placed yellow sticky card traps in their home gardens for two 7-day sampling periods in June and August of 2009 and 2010. After each 7-day collection each volunteer examined their card for 14 different lady beetle species and filled out a data sheet indicating which species were present. They then sent us their data sheet and yellow sticky card so that all identifications could be verified and additional insects could be counted. To see images of these species check out our lady beetle ID guide.

In a future post I will review the diversity and relative abundance of lady beetles found but today I want to talk about how well the volunteers were able to distinguish between these tiny insects. Overall, volunteer identification accuracy of lady beetles in 2009 was 46.2% in June and 50.3% in August. Similar accuracy rates were found in 2010, with 51.1% of lady beetles correctly identified in June and 43.1% of in August. While this may seem discouraging to some of our volunteers, I think its a really positive finding that we can build on in the future. Each volunteer who participated in our survey attended a 2-hour training session. At these sessions we used a power point presentation to illustrate how to identify each species. We also had boxes of pinned insects. I think that this year I am going to bring examples of actual sticky cards collected in 2010 so that volunteers can see what the lady beetles look like on the cards, when they can be much more difficult to ID. We may also try and get some photos of lady beetles on sticky cards on the website for reference.

I also plan to target additional time towards discussing species which were most commonly confused. The multi-colored Asian lady beetle (Harmonia axyridis) was the most abundant of all species found in Ohio gardens. Volunteers incorrectly identified H. axyridis as ten other lady beetle species. Forty specimens (18.6% of specimens collected) were incorrectly identified as a native coccinellid, with the rare convergent lady beetle (H. convergens) accounting for 20 of these errors across the four sampling periods. Twenty H. axyridis specimens (9.3% of specimens collected) were incorrectly identified as another exotic species. Of these 17 were identified as the seven spotted lady beetle (C. septempunctata). Some also missed H. axyridis specimens on their yellow sticky card trap (13 specimens, 6.0% of total collected) or listed it as “other lady beetle” (20 specimens, 0.3% of total collected) indicating that they thought H. axyridis was a lady beetle species other than the 14 surveyed by the BLBB program.

I am not surprised that volunteers had difficulty identifying this species. It is called the multicolored Asian lady beetle because it varies in color from pale yellow to bright red. Some individuals have spots and others lack spots. The key identifying feature of this insect is a black "W" on the pronotum, a plate covering the insect's thorax. Michelle and Andy who follow our blog sent us some great pictures of the multicolored Asian lady beetle, check out our March 2010 blog post to learn more about this species.