Species Early/Late Dates by Year

Hopefully you have noticed a section called Flight Period in our pages describing all the butterfly species found in New Jersey. Included there for each species are the earliest and the latest dates that have ever been recorded by our observers. Of course, the dates of the first and last observation of each species changes from year to year. For those who are interested in studying how these dates compare from year to year, two spreadsheets are available containing this information.

The North Jersey spreadsheet is maintained by the New Jersey Butterfly Club. For the years 2012 through the present its data are extracted from the sightings reported to the North Jersey Recent Sightings website, which covers Mercer and Monmouth counties and northward. For 2011 and earlier the data comes from the Pearly-Eye a print publication of the club begun in 2001. North Jersey observations were not recorded prior to 2001, and few reports were made to the Recent Sightings page from 2012 through 2015.

The South Jersey spreadsheet covers Burlington and Ocean counties and southward. It is maintained by our colleagues who run the South Jersey Butterfly Project. From 2008 through August, 2015 all their observations were stored using the Google Sheets application. For September, 2015 and later the South Jersey Recent Sightings website came into use. Subsequently all the old Google Sheets data were loaded in the Recent Sightings system.

On both spreadsheets you will notice that the first two columns following the species name contain the all-time earliest and latest dates for each species. The following columns show both the earliest and latest dates that each species was observed for every year for which data is available. The cells with the extreme early and late dates are color coded to allow you to determine in which year(s) these dates occurred. Finally while they are readable when using a smart phone, these spreadsheets are rather large, so they don't display in an ideal manner on such devices. Viewing will be much easier on devices with larger screens.

North Jersey Early/Late Dates

South Jersey Early/Late Dates