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Friday, July 13, 2018

Gray Hairstreak butterfly – Strymon melinus

Gray Hairstreak butterfly (Strymon melinus): perched on Ashyleaf buckwheat.

July is a great month for butterflies, with many species at their peak numbers. Gardeners who have chosen plants to attract butterflies are justly rewarded this month.  Due to our continuing Western drought, gardens are becoming ever more important for beneficial insects (like butterflies).  To learn more about gardening for butterflies see: http://mother-natures-backyard.blogspot.com/2012/06/butterfly-gardens.html

Among the first butterflies noticed by many gardeners are the big, showy species like the Monarchs, Gulf Fritillaries and Swallowtails.  But equally interesting – and important to the garden ecosystem – are the smaller butterflies.  One of our favorites is the Gray Hairstreak - Strymon melinus. 

The Gray Hairstreak is a common species in most parts of the continental U.S. and south to Venezuela. It’s the most common Hairstreak seen in many gardens; you may have noticed it in your own garden, particularly if you grow flowering plants.  Strymon melinus is one of our smaller butterflies, with a wingspan of 7/8 - 1 3/8 inches (2.2 - 3.5 cm).  Like the Swallowtails, the Gray Hairstreak has a single ‘tail’ on the hindwing.

Gray Hairstreak butterfly (Strymon melinus):
feeding on Ashyleaf buckwheat (Eriogonum cinereum)
When perched or feeding, a Hairstreak’s wings are usually closed, making the underside of the wing more commonly visible.  The underside is mostly gray, with spring and fall flying adults a darker gray than those of summer.  On close observation, the wings have a thin, pale fringe and thin rather straight black and white band near the edges of both the fore (front) and dorsal wings.  More conspicuous is a darker, more irregular band of blotches that are white, black and orange (see below).  Gray Hairstreaks also have two large orange and black splotches on the hindwing.
Gray Hairstreak butterfly (Strymon melinus):
close-up of underside of wings
The Gray Hairstreaks we’ve seen have dark eyes and light-and-dark banded antennae with an orange tip.  The heads often have a patch of orange on the back of the head.  The abdomen of females may have a red or orange tinge.  The upper-side is blue-gray with a large orange-red spot near the ‘tail’.  For more good photographs see refs. 1-5, below.

The larvae (caterpillars) have the typical form of Hairstreak larvae.  They are rather flattened, with distinct segments and a slightly tapering abdomen.    Color can range from almost gray through tan, green and even rosy pink or purple.  Earlier chrysalids hatch 7-10 days after pupating (forming a cocoon); fall ones hibernate over winter.     Unfortunately, we don’t have any photos of the larvae or chrysalids.  For excellent photographs – plus advice on raising Strymon melinus – see reference 6.

Gray Hairstreaks can be seen much of the year in warm climates.  They have two flights (sets of hatchlings) per year in colder climates and at higher elevations (May to September).  They often have 3-4 flights (February-November) in warm climates like the lower elevations of S. California.  Males can be seen perched on warm afternoons, waiting for receptive females.   Eggs are laid on the flowers of a variety of host plants – most often in the Pea (Fabaceae) or Mallow (Malvaceae) families.  The young larvae eat mostly flowers and fruits; later stages may eat leaves as well.  In agricultural areas, this species may become a minor pest on bean and cotton crops. [5]

Gray Hairstreak butterfly (Strymon melinus):
 on Eriogonum parvifolium
In our gardens, we most often see males perched on upright stems or leaves - or individuals feeding on a wide range of flowers.  Perched individuals often rub their wings together – a behavior commonly seen in Blues, Coppers and Hairstreak butterflies.  The reason for this behavior is unknown; it may be a defensive mechanism, drawing attention to the abdomen rather than the head.  But whatever the purpose, it’s an interesting behavior to observe.
Gray Hairstreak butterfly (Strymon melinus): nectaring on
 Ashyleaf buckwheat. Note long, thin proboscis.
Gray Hairstreaks inhabit a wide range of sites, in large part due to their relatively unspecific food requirements.  Adults obtain nectar from many plant species.  In our gardens, the most popular seem to be the native Buckwheats (Eriogonum species), the Mints (including Salvias), the many-flowered Sunflowers (Goldenrods,  Goldenbushes and Telegraph plant), Milkweeds and clovers.  We’ve also seen them on Globe Gilia (below) and they are known to frequent other native and non-native garden flowers.

Gray Hairstreak butterfly (Strymon melinus):
 on Globe gilia (Gilia capitata), Mother nature's Backyard.
The larvae are also less selective in their food requirements than many native butterflies.  The host plants are mostly herbaceous annuals and perennials, commonly in the Pea or Mallow families.  Recorded local host species include garden beans (Phaseolus), native Lotus species, clovers (Trifolium species), Amorpha (false indigo), mallows (including hibiscus), Humulus (hops), Polygonum species, Eriogonum (Buckwheats), Salvia (Sage) species and cotton.  There likely are other host plants, yet to be discovered.  Grow any of these to provide an incentive for Gray Hairstreaks to live in your garden.

So what role do Gray Hairstreaks play in the open woodlands, prairies, parks and gardens in which they reside?  First, they act as minor pollinators for the flowering plants they visit.  They are not the most important – that role goes to bees and pollinator flies. But they do their part by increasing the diversity of pollinator species, helping to insure the livelihoods of insect pollinated plants.  In addition, the larvae of all butterflies and moths are an important source of protein for birds and even some insects. 

Gray Hairstreaks also contribute to the beauty and interest of local gardens.  They are fun to watch and observation can be done close to home.  You may want to record your observations – and send your photos to iNaturalist (https://www.inaturalist.org/). You may even discover a new host plant for Strymon melinus – right in your own backyard!





We encourage your comments below.   If you have questions about garden butterflies or other gardening topics you can e-mail us at :  mothernaturesbackyard10@gmail.com


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