The September dragonfly migration is in full swing, often accompanying hawks and attacked by kestrels for a quick snack when they happen to share the ridge-top migration routes.
Separately, biological/behavioral curiosity about these insects struck me yesterday as for the first time I was able to witness large, adult dragonflies foraging on the fly. There was a sunbeam shining through overhanging trees to some mowed grass in a generally shaded area. A dozen back-lighted dragonflies were darting back and forth and up and down in the light. Upon closer inspection I noticed some type of small hatch rising from the grass to heights of about 8 ft before flying out of the sunbeam. It was a low density hatch that was also back lighted so individual insects could be observed and it was interesting to see the dragonflies dart up and down as well as make u-turns to intercept individual smaller insects. They sometimes missed and made a u-turn to correct their errors.
This morning I decided to do a little research and found that one of the common migrants in Pa is the green darner, which flies to the southern gulf coast, the Caribbean, and to Mexico. They can cover up to 80 miles in a day. Because the water is warm there, they mate, lay their eggs, eggs hatch, nymphs go through all instars in perhaps 5-6 months, and these new adults fly north as far as Canada in spring. In cold water of the north, dragonfly life cycles of other species can take up to 5 yrs.
While this was of personal interest, it’s also fascinating enough info that I think kids and teens will like some of the info during the annual Berks Co Fed of Sportsmen’s June field day. Eighty to ninety kids and teens in groups of 10 (plus their parents sometimes) get 40 min of exposure to aquatic insect and macroinvertebrate identification, ecology, life cycles, and foraging behavior as they circulate in groups from instructional station to instructional station. Note: The field day is NOT limited to Berks Co residents and it’s free.
Separately, biological/behavioral curiosity about these insects struck me yesterday as for the first time I was able to witness large, adult dragonflies foraging on the fly. There was a sunbeam shining through overhanging trees to some mowed grass in a generally shaded area. A dozen back-lighted dragonflies were darting back and forth and up and down in the light. Upon closer inspection I noticed some type of small hatch rising from the grass to heights of about 8 ft before flying out of the sunbeam. It was a low density hatch that was also back lighted so individual insects could be observed and it was interesting to see the dragonflies dart up and down as well as make u-turns to intercept individual smaller insects. They sometimes missed and made a u-turn to correct their errors.
This morning I decided to do a little research and found that one of the common migrants in Pa is the green darner, which flies to the southern gulf coast, the Caribbean, and to Mexico. They can cover up to 80 miles in a day. Because the water is warm there, they mate, lay their eggs, eggs hatch, nymphs go through all instars in perhaps 5-6 months, and these new adults fly north as far as Canada in spring. In cold water of the north, dragonfly life cycles of other species can take up to 5 yrs.
While this was of personal interest, it’s also fascinating enough info that I think kids and teens will like some of the info during the annual Berks Co Fed of Sportsmen’s June field day. Eighty to ninety kids and teens in groups of 10 (plus their parents sometimes) get 40 min of exposure to aquatic insect and macroinvertebrate identification, ecology, life cycles, and foraging behavior as they circulate in groups from instructional station to instructional station. Note: The field day is NOT limited to Berks Co residents and it’s free.
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