June Insect Phenology

by Carl Strang

As I described in the previous post, plant phenology this year has been marching along in its usual pattern of between-year convergence of first flower dates. The results for insects in June were less consistent, and therefore more interesting. First appearance dates of 17 insect species in June were a median 11 days later in 2013 than in 2012. This is not surprising, given last year’s early season. There was some convergence, as that difference was 33 days in May.

The first sighting of Bombus auricomus at Mayslake Forest Preserve was on June 14 this year.

The first sighting of Bombus auricomus at Mayslake Forest Preserve was on June 14 this year.

No such convergence appeared in the comparisons of 2013 with 2011 and 2010, where the June median was 11 days later this year than in 2011 (19 species), and 9 days later than in 2010 (19 species). The differences in May were 10 days in each case, so no change. The median showed no difference (0 days) between June first appearances in 2013 and 2009 (19 species); in May that difference was 5 days.

The first monarch butterfly arrived from the South on June 13 (and yes, this is a photo from an earlier year).

The first monarch butterfly arrived from the South on June 13 (and yes, this is a photo from an earlier year).

We had some warm weather, but on the whole this spring was cool and often rainy. I think that weather pattern probably accounts for 2013’s continued lateness through June, and the relative lack of convergence to date.

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