The Sachem immigrates from the south every year, and occasionally makes it as far as central New Jersey.  I've seen it in past years, but haven't been able to identify it until 2002.  Although there were lots of them in the garden that year, it usually isn't very numerous.  It failed to make an appearance in 2003, and I only saw one or two in my garden last year.  However, they were fairly numerous at the Rutgers Display Gardens.  The top three pictures on the left are females, and the rest are males.