Summer Garden Visitors

As the summer heats up, flowers bloom, and our vegetable "babies" grow, we notice a number of summer garden visitors and residents. Read on to find out how the population and behaviors of creatures in our gardens change as the summer progresses.

Firefly season in Pennsylvania peaks in June and July, with a few adults lingering until August. Fireflies (Photuris pensylvanica) are Pennsylvania's state insect, and sixteen species reside in the state. Fireflies live as adults for about a month before laying eggs and dying. The eggs hatch after three weeks, and the next one to two years are spent as larvae in the soil and leaf litter. If you happen to see firefly eggs and larva, they might be glowing just like the adults! Unfortunately, though, these marvelous insects are on the decline due to loss of habitat, light pollution, and use of pesticides. You can help support the firefly lifecycle by reducing unnecessary outdoor lights during firefly breeding season, reducing the use of pesticides in your lawn and garden, and leaving leaf litter and soil undisturbed at the end of the season. For more information, refer to Firefly Conservation and Research.

For those venturing out in the early mornings, it may seem like the grass spiders and orb weaver (Araneidae spp.) spiders are taking over. Dew captured on grass clearly outlines all of the new grass spider webs. Grass spiders (Agelenopsis spp.) are a manicured lawn's friend, as they will snack on all sorts of insect pests that would feast on the grass. Orb spiders, on the other hand, will suspend large ovoid vertical webs, and re-cast them every evening for maximum efficiency in catching flying insects...and entangling the unwitting pedestrian.  Anyone who has encountered the yellow garden spider (Argiope aurantia) will recognize the famous zigzag pattern in the web. This spider is intimidating, but rarely bites humans and is mostly harmless. Why are there so many spiders in summer? It has everything to do with their life cycle. In spring, the spiderlings are hatching, evading predators, eating and growing; by July and August, they are large enough to start the next step of their life-cycle, including web spinning and laying their own eggs to continue the circle before they die in the fall and winter. Take heart, web spinning decreases as prey species die off in the cool of the fall.

As the day heats up, gardeners report more frequent sightings of pollinators in July and August, including hummingbird moths (hawkmoths or sphynx moths Sphingidae spp.), swallowtail butterflies, wasps, bees, and flies. The publication Adult and Larva of Moths in Pennsylvania will help you identify the many types of moths that you see in summer. In the case of most butterflies and moths, overwintering occurs as a caterpillar or pupae, and the first generation occurs in spring. The second generation matures in July and August and will lay eggs that hatch, pupate, and overwinter. For this reason, skipping fall garden clean-up provides respite for the gardener and habitat for next year's butterflies, whose pupae are hiding in gardens' end-of-season detritus and leaf litter. Want to be a citizen scientist for moths and butterflies?  Visit Butterflies and Moths of North America and create your account to contribute your observations, specifically high-quality pictures of eggs, larvae, or adults along with location data.

Make sure you get a good look at the specimens in your garden, though, as hawk moths are often mistaken for hummingbirds. Hummingbirds arrive in Pennsylvania in late April and early May (Pennsylvania Game Commission Ruby-Throated Hummingbird notes), and by July and August we may see young birds from the first brood of the year as well as parents preparing for a second brood. If you are interested in feeding hummingbirds, the Pennsylvania Audubon society offers hummingbird feeder tips. The privately-managed Hummingbird Central site also reports on the annual migration of hummingbirds, which typically reside in Pennsylvania from April to October.

The presence of wasps and bees also become more obvious in the height of summer. Wasps and hornets are hunting soft-bodied insects, such as aphids and caterpillars, and their appearance coincides with the increase of prey. See this information on the bald faced hornet. They act as pollinators as they visit flowers and plants, as they also feed nectar to their colonies.  Yellow jackets make more of an appearance in August; the queen stops single-handedly feeding the colony as her reign comes to an end, and workers are the first to be cut off. This drives them further into their territory and your barbeque, looking for food.

Cicadas (loudly) make themselves known at summer's peak, too. Annual cicadas first emerge around May from their underground burrows where they have been overwintering from the previous year. Periodical cicadas can also erupt at the same time, but these cicadas were previously underground for thirteen or seventeen years, depending on the species.  (Both are members of a superfamily of insects—Cicadoidea.) Pennsylvania is home to nine species of annual cicada who are warming up to serenade prospective mates. Annual cicadas will spend about six weeks above ground out of a life span of three to five years.  This brief window in the sun is spent as adults. Adult female cicadas will lay around 500 eggs that hatch in six to seven weeks as nymphs that drop to the ground to burrow.  Some report using the song of the cicada to predict the temperature of the day—the earlier the cicada sings, the hotter the day will be. While a lovely thought, no studies have supported this folklore.

Where there are cicadas, there are also cicada killers (Sphecius speciosus). This scary looking yellow and black banded wasp is very large and some may confuse them with the reports of the "murder hornet," actually the Asian giant hornet. (To be clear, there are no Asian giant hornets in Pennsylvania; all reports are from the Pacific Northwest.) The cicada killer is a gentle wasp and has two priorities in July and August: digging burrows for her solitary eggs and collecting cicadas to feed her young. The cicada killer wasp prefers to burrow in dry, sandy soil.

For more information on invertebrates discussed in this article and how to help support them, visit The Xerces Society for Invertebrate Conservation.