Sunday, August 7, 2011

Hornworm or what a hummingbird moth looks like before its metamorphosis

Back in 2005, the year after the Home Bug Garden got its first major additions of expensive perennials (and the year after most were striped half bare of leaves by the hail from the two '1 in 200 year storms'), our new flowers were visited by several Hummingbird Clearwing Moths (Hemaris thysbe Fabricius, 1775). The moths proved too fast for our cameras, but other photographers at BugGuide have posted several excellent pictures. The day-flying moths look more like giant bumblebees to me than hummingbirds, but they can hover very well and are the right size for hummers.

A few weeks later, we were aghast when we noticed two inch-long green horned-devils stripping our struggling highbush cranberry and nannyberry bushes. Urr, arghh - the first real challenge to our pretense of gardening for bugs. We decided on a compromise in this first skirmish and deported half the caterpillars to outside the yard to fend for themselves and let the other half feed away to pupation. It turns out we need not have worried so much about our highbush cranberries - all but one scraggly survivor have been destroyed by another day-flying moth, Synanthedon fatifera, the viburnum crown borer. The adults appear to be mimicking a spider wasp in this case. The caterpillars bored in the crowns of our highbush cranberries killing a third to a half of the canes each year until I had to grub out what rotten bits of persistent crown were left.

Fortunately, the borers don't seem to be interested in our nannyberry (now nearly 3 m tall), nor did the hummingbird moth. But when a friend on AlbertaBugs pointed out that he had the caterpillars on his viburna, we checked and lo and behold we have them again. This time we will let them eat all they want - there are lots of leaves and only a handful of hornworms - and just be happy they are still around.

As well as welcoming back an interesting bug, this posting was designed to follow-up on what I learned at a post at Alex Wild's new blog at Scientific American, The Compound Eye. Among other things, Alex boldly states that to post an image to its best effect "Every blogger should know their column width, in pixels. " I don't seem to be clever or persistent enough to find this information on my blog, but a little experimenting indicates that a 600 pixel wide image as above is not auto-crunched by Blogger. I highly recommend The Compound Eye to anyone interested in getting the most out of their insect photography.

1 comment:

  1. Must check my viburnum!

    Thanks for the Wild link...don't know how I missed the arrival of his new blog.