Strymon melinus

Ge­o­graphic Range

Gray hair­streaks can be found in South­ern Canada to Cen­tral Amer­ica and North­west­ern South Amer­ica. They occur from coast to coast and in a va­ri­ety of al­ti­tudes rang­ing from sea level to nine thou­sand feet. (Carter, 1992; Tveten and Tveten, 1996)

Habi­tat

Un­like most but­ter­flies, gray hair­streaks do not pre­fer one spe­cific habi­tat. They are wide­spread in trop­i­cal forests and open, tem­per­ate wood­land areas. They can also be found in mead­ows, crop fields, ne­glected road­sides, and res­i­den­tial parks and yards are often homes of this fas­ci­nat­ing but­ter­fly. (Carter, 1992; Milne and Milne, 1980; Scott, 1986; Tveten and Tveten, 1996)

  • Range elevation
    0 to 2745 m
    0.00 to 9005.91 ft

Phys­i­cal De­scrip­tion

In the ear­lier stages of the life cycle, gray hair­streaks are straw, pur­plish-white, pink, red­dish-brown, or green lar­vae with var­i­ous other paler marks. The head is yel­low­ish-brown. Throuhout Texas, how­ever, the lar­vae have been noted to be en­tirely green and cov­ered with short hairs. The pupae hi­ber­nate and are usu­ally brown­ish in color. In the adult stages of the life cycle the but­ter­fly's upper wings are dark gray­ish brown with a promi­nent or­ange spot lo­cated at the outer mar­gin close to the shorter of the two black­ish tails. The con­spic­u­ous or­ange spot is larger than most Stry­mon species. The hind wing is gray (darker in males and spring adults than in fe­males and sum­mer adults). It too has a black-eyed or­ange spot at the bases of the hind­wing tails. There is a small patch of blue be­fore the tail, and two bro­ken cross­bands of black and white spots. The male ab­domen is or­ange. The wingspan varies from 2.6 to 3.65 cm. (Carter, 1992; Milne and Milne, 1980; Scott, 1986; Tveten and Tveten, 1996)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • Range wingspan
    2.6 to 3.65 cm
    1.02 to 1.44 in

De­vel­op­ment

After about six days the eggs hatch, and over the next twenty days the cater­pil­lars grow and de­velop. They then form a chrysalis and after about ten days emerge as adults. Sil­very-blues spend the win­ter as pupae and can have three or more gen­er­a­tions per year. De­vel­op­ment time can vary greatly de­pend­ing on ge­og­ra­phy and the dif­fer­ent hosts. (Drees and Jack­man, 1998; Scott, 1986; Tveten and Tveten, 1996)

Re­pro­duc­tion

Mat­ing and egg-lay­ing occur in early spring. Adult males perch on small trees and shrubs from early af­ter­noon to dusk to await fe­males. They usu­ally perch at a level where they can catch cooler breezes, lower to the ground in the spring and higher as the year goes on. Males back dor­sally. Mat­ing pairs are nor­mally spot­ted at night, and fe­males oviposit dur­ing the midafter­noon. The fe­males then lay their pale green eggs on hosts' buds or newly opened flow­ers of the host plant. (Drees and Jack­man, 1998; Scott, 1986; Tveten and Tveten, 1996)

  • Breeding season
    early spring

There is no parental in­volve­ment once eggs are laid.

  • Parental Investment
  • pre-fertilization
    • provisioning

Be­hav­ior

The adults are quick fliers and are seen most often be­tween the months of May and Sep­tem­ber. They like to bask in the sun with wings spread wide, un­like most hair­streaks, but they also rub their hind­wings to­gether in the typ­i­cal fash­ion of most hair­streaks. This back-and-forth move­ment makes the wings look like an­nten­nae, ap­par­ently to fool preda­tors into at­tack­ing a less vital part of their body. They are best seen when at rest and their wings are folded to­gether over the back, one hind wing some­times raised while the other is low­ered. (Drees and Jack­man, 1998; Milne and Milne, 1980; Tveten and Tveten, 1996)

Food Habits

Just as in many other char­ac­ter­is­tics of gray hair­streaks, their food habits are gen­eral. Nei­ther the cater­pil­lar nor the but­ter­fly are spe­cific to any cer­tain plant or flower, but rather feed on a va­ri­ety of plants. The lar­vae eat from at least twenty dif­fer­ent fam­i­lies of plants, in­clud­ing the pea and mal­low fam­i­lies. Nor­mally they can be found eat­ing fruits and flow­ers. They can also be found on maize, cot­ton and a va­ri­ety of shrubs and trees. The but­ter­fly feeds on nec­tar from a wide va­ri­ety of flow­ers. (Carter, 1992; Milne and Milne, 1980; Scott, 1986; Tveten and Tveten, 1996)

  • Plant Foods
  • leaves
  • fruit
  • nectar
  • flowers

Ecosys­tem Roles

These gen­er­al­ists feed on (and likely pol­li­nate) a wide va­ri­ety of plants. They also may be eaten by a wide va­ri­ety of preda­tors.

  • Ecosystem Impact
  • pollinates

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Gray hair­streaks ben­e­fit hu­mans just as so many other but­ter­flies, bees, and small birds do. The but­ter­fly par­tic­i­pates in a mu­tu­al­is­tic re­la­tion­ship with many flow­er­ing plants by re­ceiv­ing nu­tri­ents (nec­tar) and act­ing as a pol­li­na­tor. (Milne and Milne, 1980; Tveten and Tveten, 1996)

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

The lar­vae of gray hair­streaks, when abun­dant, can be­come pests to com­mer­cial crops, in­clud­ing cot­ton, beans, corn, and hops. Habits such as these have earned the cater­pil­lar the com­mon name of "cot­ton square borer" and "bean ly­caenid". (Milne and Milne, 1980; Tveten and Tveten, 1996)

  • Negative Impacts
  • crop pest

Con­ser­va­tion Sta­tus

Gray hair­streaks are not cur­rently en­dan­gered or threat­ened.

Other Com­ments

This but­ter­fly is so abun­dant across the United States that some sug­gest that be­sides the monarch it should be named the na­tional but­ter­fly. (Tveten and Tveten, 1996)

Con­trib­u­tors

Matthew Wund (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Lau­ren Ro­driguez (au­thor), South­west­ern Uni­ver­sity, Stephanie Fab­ri­tius (ed­i­tor), South­west­ern Uni­ver­sity.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

diapause

a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

frugivore

an animal that mainly eats fruit

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nectarivore

an animal that mainly eats nectar from flowers

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

suburban

living in residential areas on the outskirts of large cities or towns.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

Ref­er­ences

Carter, D. 1992. But­ter­flies and Moths. New York: Dor­ling Kinder­s­ley.

Drees, B., J. Jack­man. 1998. A Field Guide to Com­mon Texas In­sects. Hous­ton: Gulf Pub­lish­ing Com­pany.

Milne, L., M. Milne. 1980. The Audubon So­ci­ety Field Guide to North Amer­i­can In­sects and Spi­ders. New York: Al­fred A. Knopf, Inc..

Scott, J. 1986. The But­ter­flies of North Amer­ica: A Nat­ural His­tory and Field Guide. Cal­i­for­nia: Stan­ford Uni­ver­sity Press.

Tveten, J., G. Tveten. 1996. But­ter­flies of Hous­ton and South­east Texas. Austin: Uni­ver­sity of Texas Press.