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Predictable Harvester

Predictable Harvester
Ranger Steve

Animals have mysterious routines we know little about to keep their bodies and minds fit. From early to late afternoon the Harvester visits selected roosting locations. It is a small butterfly with brown and tan undersides of wings that are visible when it stands on a leaf with wings folded upward over its back. A number of irregular silver lines or circles loop on the wing outlining brown speckles.

The top of wings can be viewed when the butterfly partially opens them. The upper wing has large patches of orange bordered in black. How color patterns aid survival is mostly unknown to me. Colors help with mate or rival recognition. 

Observations indicate predictable activity periods. I do not see the Harvester in the roosting area until afternoon and it continues a presence into late afternoon. The butterflies perch on shrub leaves about five feet above the ground along the north side of a forest clearing where sun glistens on leaves. There it stands patiently waiting. Later in the day it perches at the east border of the clearing when sun rays brighten leaf landing pads.

Apparently the butterfly has business elsewhere in the morning. Perhaps it travels to speckled alders and ash trees on the floodplain where wooly aphids suck juices from tender stems. Harvesters lay eggs among the white wooly wax covering aphids create and use it to cover their bodies. When the caterpillar hatches, it covers its body with the waxy fluff and begins eating aphids. It is concealed and camouflaged from its predators by the wax and eats peacefully controlling aphid numbers. 

The caterpillar develops rather quickly, pupates and soon emerges as an adult butterfly. 

I visit the butterfly’s afternoon roosting site daily on walks. When a second one flies near, it darts toward it. It could possibly be a suitable mate or rival male. 

Last year there were three broods. Spring, summer, and fall broods were present. The spring brood flew 31 May through 21 June. The summer brood flew from 19 July through August and the fall brood began in August and overlapped with the summer brood. Harvesters were present through 26 September. This year the spring brood began flight on 31 May and was only noticed until 6 June. A long gap occurred until the summer (or fall?) brood began on 5 Aug. That brood continues at this writing in late August. 

The Harvester is the only predatory caterpillar found in the United States and it aids rapid development. Others are vegetarians and mature more slowly. Every species has something uniquely special.

Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at odybrook@chartermi.net – Ody Brook Nature Sanctuary, 13010 Northland Dr. Cedar Springs, MI 49319 or call 616-696-1753.

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