As the lazy, hazy days of summer are upon us there are distinct changes in the pace of natural life. The bulk of bird breeding activity is over and fall migration has begun. But insect activity is intense. In particular I notice that bumblebees are everywhere and industriously collecting pollen and nectar. I am especially pleased that native bees vastly outnumber the exotic European honeybees in our area. Bumblebees have a big advantage on days with cool mornings since they can maintain an elevated body temperature by metabolic means and start foraging earlier than the late rising butterflies which typically are not very active until about 10 am. Favored flowers tend to be asters or composites, which have very advanced “flowers” made up of numerous individual disc and ray flowers. The orange cosmos and purple cone flower shown here are good examples of this unusual trait which has made aster family flowers very successful.
Although monarch butterflies have been rather scarce in most areas, we have reasonable numbers in our area of the Blue Ridge mountains perhaps because of many thousands of nectar sources in both native and planted flowers, and numerous young common milkweeds (Asclepias syriaca) in our hay fields. Monarch caterpillars require tender young leaves whereas milkweed tussock moths prefer the older leaves. We are experimenting with a novel means of providing monarchs with young milkweed leaves in the latter half of summer by cutting the hay only once in late June/early July and allowing milkweeds to re-grow along with summer grasses which provide very important food and cover for birds in late summer, fall and winter. The photo shows one such field which was cut July 11 and by Aug. 25 the milkweeds are already in bud. Although some meadowlark nests may be destroyed, they will likely re-nest and all birds will benefit greatly by the provision of seeds and cover from warm season grasses.
One of the most spectacular means of attracting butterflies is by planting butterfly bushes (Buddleja or Buddleia), a shrub from China that produces large amounts of nectar. Although this plant can be invasive in some areas, that is not so in many regions and you can reap the rewards of having legions of butterflies visit your yard. This photo shows a spicebush swallowtail nectaring on one of the many varieties available. This swallowtail is one of the group of “black and blue” butterflies that mimic the toxic pipevine swallowtail for protection against predatory birds.
One of the many interesting summer insects is this tachinid fly which I found buzzing near me on our porch. When you heard a loud buzz you pay attention since the bug may want to bite you! This critter may be scary looking but is harmless to humans yet deadly to caterpillars. It is termed a parasitoid since its larvae live inside caterpillars and eventually kill them, unlike most parasites which live with a live host. Relatives of this native fly have been introduced to control gypsy moths with unfortunate results since they also ate native silkmoths. The ultimate results of such biocontrol efforts can be difficult to predict. Ecology is not rocket science, it is far more complicated!
Many plants have produced berries during the summer and the black cherry trees are loaded with fruit. Many birds feed on this fruit perhaps including swarms of migratory tree swallows which have landing in our cherries.
So enjoy the remainder of summer and its special charms. The fall is coming soon with major changes in the natural world.