Gray Hairstreak Butterflies in Your Garden

If you watch carefully, you may notice lovely little hairstreak butterflies in your summer garden. A member of Lycaenidae, the second largest family of butterflies with over 6,000 species worldwide, the gray hairstreak (Strymon melinus) can be found from southern Canada to northern South America. Although they’re considered common, they are rarely seen in large numbers. Since they’re small—with a wingspan of up to only about an inch and a quarter—and flighty, they can be easily overlooked.

Male and female gray hairstreaks appear somewhat similar, although females have rounder and wider forewings, and a male’s abdomen during summer is pale orange toward the tip. Their dorsal wings are a bluish-gray, with an orange spot that resembles an eye—if you’re wondering why, read on. Their underside is ashy gray, with jagged bands of black lined with white, and two orange spots with black areas. There is seasonal variation in color.

“False head” pattern
When most hairstreak butterfly species land, they often perch with their head downward and their two sets of tails pointed upward (Winkler 1977). They have what’s known as a “false head” at their rear end (as far from their real head as possible), complete with tiny hindwing tails that masquerade as fake antennae. When they move their hind wings up and down in a sawing motion (Sourakov 2017), they attract attention to the rear wing — instead of their real head and body — which serves to deflect predator attacks. Those big “eyes” and moving “antennae” either scare away small would-be attackers, or trick other predators into attacking the wrong end of the butterfly so that the expendable part of the wings may be torn away and allow the butterfly to escape without mortal wounds.

It’s easy to assume that this defense would help hairstreaks survive attacks by birds and possibly larger invertebrates, and a 2013 study by Dr. Andrei Sourakov at the University of Florida demonstrated that the false head on the wings of the red-banded hairstreak allowed it to escape attack by a species of jumping spider, a predator with great eyesight (and an adorable face, close-up).

Large menu
Since gray hairstreaks are very widespread, they do not have a strong preference for host and nectar plants like many other lepidoptera species do, and they even do well in disturbed habitat like urban areas as long as it offers food, shelter, and sunlight. Adults feed on nectar from a variety of plants (often with short, tubular, composite flowers), including native goldenrod, wild onion, milkweed, dogbane, mint, etc. The male pictured below has found a patch of native yarrow (Achillea millefolium var. occidentals). Caterpillars’ menu reportedly includes hundreds of hosts in dozens of plant families, especially legumes, roses, and mallows, but also oaks, pines and strawberry plants. Young caterpillars eat flowers and fruits, while the older ones (at the final instar) may consume leaves. They pupate in a sheltered location like a curled leaf, and overwinter as pupae (James and Nunnallee 2011), possibly in wood piles, beneath loose bark, or in hollow trees or logs.

Relationship with ants
Speaking of good things to eat, many hairstreaks, including the gray, have a special mutualistic relationship with ants (known as myrmecophily), who use the caterpillars as a host of sorts, from which they harvest a nutritious liquid full of sugars and amino acids via the caterpillars’ dorsal nectary organ. In exchange for the yummy meals, the ants guard the caterpillars from predators throughout their larval life, and, needless to say, don’t eat the caterpillars themselves. So the next time you’re annoyed by ants, remember that they may be attending and protecting little caterpillars!

© 2021 Eileen M. Stark

Take Care During Fall (and Spring) Garden “Clean-ups”


The last of the warm, dry fall days are upon us
and it seems like a great time to be puttering around the garden. But this time of year is actually not a good time to be “cleaning up”—that is, removing fallen leaves and woody debris from bare soil, pruning standing plants, and making your yard look somewhat like a victim of a gardening magazine makeover. Leaves and other plant material that fall to earth are part of nature’s systems that nurture and shelter wildlife and enrich and protect the soil. Healthy soil has an uncanny ability to not only keep plants thriving, but also store carbon.

Bedtime for bugs
Leaving fallen leaves on soil is one of the best (and easiest!) things you can do to support wild ones such as birds, amphibians, and small mammals in your garden, as well as myriad invertebrates, including bees, butterflies, spiders, beetles, and worms. Leaves and other plant matter are meant to fall to the soil, to provide food for unfathomable numbers of microbes as well as the macroscopic consumers and recyclers that feed on decaying plant matter. Further up the food chain, many creatures—ground-feeding birds, for example—rely on nature’s soil cover to provide for those they need to eat, which they find under leaves and downed wood (fallen twigs and branches, etc.).

Fox sparrow

A fox sparrow finds dinner under leafy cover.

If we zoom in a bit, we might see small organisms, such as syrphid fly larvae depending on plant debris for a sort of blanket to help them through the cold, wet winter. As things warm up in springtime, some kinds of syrphid fly larvae will consume enormous quantities of aphids and leafhoppers that can harm our edible plants. Adult syrphid files (also called “hover flies” or “flower flies”) are important pollinators: spring through late summer I see quite a variety of them in my garden, probably because I prescribe a healthy dose of fallen leaves on the ground in autumn.

A leafy layer also encourages other pollinators to make it through the winter. For example, as pollination season shuts down and bumble bee workers (females) and males perish, newly crowned bumble bee queens (technically “gyne,” an impregnated queen who has not yet founded a nest but will establish a whole new generation of bumble bees next year) live on. Queens find refuge by digging a shallow tunnel in loose soil—known as a hibernaculum—that’s often tucked under leaf litter. And, many species of lepidoptera (butterflies and moths) overwinter under fallen leaves as eggs, larvae, pupae, or adults. If we disturb their slumber by blowing or raking them away, they and the ecosystem will suffer. Essentially, they and their habitat need to simply be left alone if we want them to grace our gardens and wilder spaces next year.

Pupa Western Tiger Swallowtail

Western tiger swallowtail pupa, clinging to wood, waits out the winter and spring.

Don’t cut back
Fall pruning isn’t a good idea because it may stimulate a plant to put on new growth, which could be sensitive to the lower winter temperatures soon to come. Another important reason not to prune in autumn is that branches and bark — particularly of native plant species — may support butterfly and moth pupae, (aka chrysalis). Swallowtail butterfly pupae pass the winter attached by thin threads to woody material — disguised as dried up leaves or old bits of wood to fool predators — until the warmer temperatures of spring stimulate their metamorphosis into adults. While some non-native fruit trees do need winter pruning and it’s beneficial to remove diseased and dying annual vegetable garden plants to prevent the spread of disease to next year’s kitchen garden, in all other parts of the yard, if you must prune woody plants, approach it the following spring, being sure not to disturb any nesting birds.

Erigeron speciosus (showy fleabane) seed head. When viewed closely, seed heads can be fascinating in their complexity.

Moreover, although they may look dead, the seed heads of PNW native perennials such as fleabane, fescue, goatsbeard, and lupine provide food for seed-eating birds, while their stems or stalks—pithy or hollow—provide shelter and/or cavity nests for beneficial insects like the wild bees that nest in small tunnels. If you must cut them back to the plants’ bases, do it as late as possible in springtime and, instead of throwing them away, place the cut stems in an out of the way place so that anyone using them to get through the winter won’t be discards and so that they may be used by the new year’s cavity nesters.

And, aesthetically speaking, allowing fading plants to stand during winter provides structure and form. On cold, frosty mornings they can be magically transformed into silvery jewels.

Protect and nourish the soil
Down at soil level, besides providing a haven for overwintering organisms, fallen leaves and woody debris protect the soil, which can degrade and erode fairly quickly from excessive rain, sunlight, and wind. In nature, soil is protected and mimicking the way it does that will help your soil stay healthy. And over many years, leaves decompose into layers of organic matter that feed plants naturally and gently, improve the condition of soil, and store carbon with the help of mycorrhizal fungi. The other day I relocated a plant to a spot in my front yard that’s been collectively accumulating a couple dozen inches of leaves over the past 15 years. To my delight I found the result of their decomposition: A couple of inches of soft, dark, rich organic matter that wasn’t there a decade ago. 

Even when we’re being careful, though, it’s easy to cause disturbance. A few autumns ago, as I moved a small amount of leaf litter to another area, I inadvertently uncovered an overwintering queen bumble bee. I felt terrible as I watched her stumble around, obviously weak and awoken from a sound sleep. Luckily it was a warm, dry day and eventually she flew off into the sunshine. But clearly the awakening had been a rude one, because a short while later she returned and burrowed into some loose soil covered by leaves, just a few feet from where she had been. After she was safely underground, I gingerly placed a couple of particularly interesting rocks several inches from her tunnel’s entrance, as well as some oak leaves on top of the soil to remind myself of where she slept.

Moral of the story: The more we clean up and work towards a neat and tidy garden, the worse off beneficial birds, bugs, and countless other life forms will be. If you tend to be a neatnik (like I am), try to catch yourself every time you start moving into manicure-mode and getting overly tidy—especially in the wilder parts of the yard where wildlife may visit or set up house. It just doesn’t make sense to risk losing them for the sake of neatness or to maintain a certain ‘look.’ If you have piles of leaves that have been raked off hardscape or lawn, here are additional ways to use them in your garden.

© 2017 Eileen M. Stark

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