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Saturday, January 13, 2007

2006 Archives: Mantid takes time to smell roses

June 15, 2006: A chinese mantid nymph cruises an iceberg rose blossom for prey a few weeks after hatching on my kitchen table June 3. Of the hundreds of hatchlings that I released into the garden, I would later see very few maturing mantids, only one adult, and no egg cases.

I had never introduced a large number of a species into the garden before, and so wondered what impact the release of hundreds of predators might have on the usual mix of spider and insect species. Of the prey, there were far fewer stinkbugs than "usual", and not nearly the numbers of katydids seen the summer before. And, through the summer of 2006, there was a marked reduction in predator populations. There were few (if any--I haven't seen even one) lynx spiders that survived the summer to maturity. There were very few araneus spiders; couldn't find any trash web spiders either. Is it possible the mantids outcompeted and preyed upon the young spiders, then were themselves preyed upon by something else? Our bird population has increased dramatically during the past year, both in numbers and diversity. Did the birds eat all the developing mantids? The
one adult mantid I saw had a deformed or injured wing, possibly from a bird attack.

Is it worthwhile to use introduced general predator species to control garden pests, or is the gardener simply displacing the natural predators already in place? It will be interesting to see what happens to the balance of species as spring and summer unfold this year.

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