Monday, November 10, 2014

An Unusual Fall for Monarch Butterflies in Arizona

Male monarch feeding on Bidens laevis in my pond October 7
Monarchs arrived on schedule in the high country of Arizona at the Grand Canyon, Flagstaff and the White Mountains this summer, but numbers were modest compared to last year's abundant population. We saw monarchs at more locations but at lower numbers when we did. With our ample monsoon rains we were hoping the population would increase as summer progressed but instead the migration through the greater Phoenix area was weak with limited sightings. Usually early September brings breeding monarchs laying eggs everywhere but this year reports were only occasional. Instead most monarchs sweeping through the area in late September and early October appeared to be in diapause with both males and females stopping to feed deeply, but had little interest in mating or oviposition despite rich stands of milkweed in bloom.

First egg-laying monarch October 24
In late October that all changed. Normally a time of diminishing monarch presence turned into a monarch explosion. Suddenly reports of monarchs soared as did breeding and oviposition. The milkweed was ready yet the fall pattern this year was rather startling compared to earlier years. Fall temperatures were warm and they likely facilitated another monarch generation locally. Heavy rains in September and warm temperatures created an ideal lush milkweed and nectar banquet and now monarchs and other butterflies are filling the skies. Instead of November, it seems like late September.

4th instar monarch larva November 9
Rather than a late larva, this is the first one of fall in my yard. At least three adult monarchs are flying every day as well as the queens, gulf frits, cloudless sulphurs, sleepy oranges and more. It's been a very unusual fall.