Bug o’the Week
by Kate Redmond

Dogwood Scurfy Scale

Howdy, BugFans,

If asked to describe a Red-osier dogwood shrub, lots of people would say “it has red bark with white lumps on it.”  It does – but it doesn’t.

Some of our most un-bug-like bugs are the scale insects.  There are lots of them worldwide – about 8,400 species in 36 families.  They’re called scales because they (the females, anyway) cling, limpet-like, to their food plant, protected under a waxy covering that looks fish-scale-ish.  They’re sexually dimorphic (“two forms”), and adult males – in the species where males exist – are often tiny and gnat-like.  If your basic definition of an insect is “six legs, some wings, and three body parts that are divided in segments” you’ll have to suspend it a bit for the scales.

Their nearest relatives are aphids, whiteflies, jumping plant lice, and phylloxera bugs.

They hatch from eggs that the female lays under her body (or they are viviparous – popped out “live”), sometimes fertilized with the help of a male and sometimes produced by parthenogenesis (“virgin birth”), and a very few species are hermaphroditic (they have dual equipment and can self-fertilize, and so a single individual can create a whole population).  Six-legged when they hatch, scales enjoy two short, mobile instars (they’re called “crawlers”), during which they disperse, but their legs are short, so they don’t go far without help (crawlers may also be blown around by the wind).  Then the tiny females settle down, attach to a host, and lose their legs, generally staying put for the rest of their lives.  The short-lived males must find females where they sit, and although he may be winged, his wings are not good for much, so he comes on foot.  There are generally several generations per year.

Scales are vegetarians, feeding on plant sap that they suck from leaves or branches.  Some are found only on specific hosts and others are more generalist feeders, and although a very few species feed on mosses, lichens, and algae, as a group, they’re fond of the woody plants.  Their predators include some ladybugs and lacewings, and a few parasitoid wasps whose larvae consume the insect (they target younger scales) or the eggs under the scale.  There are scale insects that are serious plant pests, scale insects that are used to control invasive plants, and scale insects that are “cultivated” because they’re used to produce shellacs, waxes, and red dyes. 

The two, big divisions of scale insects are “cushiony” and “armored” scales.  Cushiony scales tend to be lumpier than armored scales, and they’re permanently attached to their waxy covering.  The excess sap that they consume, released as a sweet fluid called “honeydew,” attracts other insects to feed on it, and some species of scale are cared for by ants that protect the scales from predators, harvest the honeydew, and help the crawlers find fresh twigs.  The downside of honeydew is that sooty mold grows on leaves where its sticky sweetness falls, which interferes with photosynthesis and isn’t very wholesome looking.  A species of cottony scale was featured in a BOTW years ago https://uwm.edu/field-station/bug-of-the-week/cottony-scale-family-coccidae/

Dogwood scurfy scales are armored scales, and armored scales are in the family Diaspididae, the largest scale family (2650 species).  Armored scales feed on hosts from 180 plant families.  They’re not attached to their waxy cover, are smaller and flatter than cottony scales, and they don’t produce honeydew.  Their tough – armored- coverings may be round, elliptical, or oyster shell-shaped and may have concentric rings/ridges.  The female incorporates the shed skins from her crawler stage into her growing shell, and the wax is made and shaped by a structure called the pygidium at the rear of the abdomen.  The critter below the scale has knob-like antennae, no legs, and little distinction between head and thorax.  

Not surprisingly, with so many species of armored scales, there are many different lifestyles.  In general, she lays her eggs or live young under her scale, which has a slit at the rear that allows them to exit.  Her eggs overwinter under the shelter of her scale, though she’s no longer alive when they hatch.

The BugLady saw a paper that said that some armored scales may get around by phoresy – hitchhiking – sticking to their six-legged taxi cabs (the study identified a fly, a ladybug, and an ant) with the help of a few “suction-cup”-tipped hairs on each of their legs

FUN FACT ABOUT ANT PARTNERSHIPS

An odd relationship has evolved between a species of African ant and a species of armored scale (which, remember, have no honeydew to trade for ant favors).  The ants shelter the scales in the galleries/tunnels they live in under tree bark – the ants are so specialized that they spend their whole lives there.  The scales no longer need protection from the elements or from predators, so most of them are “naked,” though some still make wax and other scale-building materials that the ants eat along with the crawlers’ shed skins and various scale “excretions.”  The whole thing hinges on the ant queen finding a suitable host tree and rounding up crawler-aged scales during her brief nuptial flight.

As the poet Muriel Rukeyser once said, “The world is made of stories, not atoms.”

SCURFY DOGWOOD SCALE/RED-OSIER SCALE INSECT

The BugLady started nibbling around the edges of this episode at least three years ago and hit a brick wall pretty fast.  The Extension and Horticultural sites mostly said – “Yup, dogwoods get scales” but offered no names or biographies, so, the original iteration of this BOTW was something like, “These are dogwood scurfy scales – they’re everywhere, but no one’s written anything about them – thanks as always to PJ at the Insect Diagnostic Lab in Madison for pointing the BugLady toward an ID.” 

But the BugLady could never do that, so…..

In her initial search for a name, the BugLady came across the pine leaf scale (Chionaspis pinifoliae https://bugguide.net/node/view/361628/bgimage) that looked similar, but she thought it was unlikely to be her scale because, well, pine needles.  The dogwood scale suggested by PJ is Chionaspis corni; in the same genus, but when you Google Chionaspis corni, most hits are for Chionaspis pinifoliae.  Bugguide.net lists no other genus members and although the dogwood scurfy scale is common here, does not even show the genus as occurring in Wisconsin (buggide’s caveat about its range maps is “The information below is based on images submitted and identified by contributors. Range and date information may be incomplete, overinclusive, or just plain wrong”).

Just to make things interesting, the accepted spelling of the genus name (since 1868) is Chionaspis, but over the years it has officially been misspelled by later taxonomists as Chianaspis, Chiomaspis, and Chionapsis.

The BugLady checked the wonderful Illinois Wildflowers website https://www.illinoiswildflowers.info/ and found the dogwood scale (along with several other species of scale including the willow scale and the Gloomy scale) mentioned in the Faunal Associations sections of the write-ups of red-osier and flowering dogwoods and several other dogwood shrubs. 

And one more thing – “scurfy” means rough or scaly or covered with scurf, and a “scurf” is a flake, scale or dandruff.

Whew!

Kate Redmond, The BugLady

Bug of the Week archives:
http://uwm.edu/field-station/category/bug-of-the-week/

Bug o’the Week
by Kate Redmond

Common Buckeye Butterfly rewrite

Howdy, BugFans,

The BugLady originally wrote about the Common Buckeye in January of 2009, but she thinks she might have given it short shrift (due to insufficient scholarship), so here’s a rewritten version with new words and new pictures.

The first thing to know about Common Buckeyes is that they are not Yankee butterflies – they are Southerners (from a largely tropical genus) that recolonize God’s Country in varying numbers from year to year and produce a two or three broods here, depending on whether spring and/or fall is long and mild.  But they are not very “freeze-tolerant,” and they can’t survive Wisconsin winters in any stage, so they wander back south in the fall.  Brock and Kaufman, in their Field Guide to Butterflies of North America, report that fall migrations of Common Buckeyes, especially on the Atlantic coast, can be spectacular.  The BugLady saw some out on the prairie as recently as a week ago – they always see her and her camera before she sees them (with their wings closed, they’re pretty well camouflaged), and they fly farther down the trail to wait for her.

The Common Buckeye (Junonia coenia, aka Precis coenia) (not the Ohio buckeye – that’s a tree) belongs to the Order Lepidoptera (“scaled wings”) which includes the butterflies and the moths.  Of the 12,000 species of Lepidoptera in North America north of Mexico, only about 700 are butterflies.  Along with the usual six-legs-three-body-parts insect stuff, moths and butterflies have in common four wings that are covered with easily-rubbed-off scales (the upper surface of a butterfly’s wing often has a different pattern then the lower surface does), and mouthparts in the form of a coiled tube called a proboscis that is used for feeding on liquids like nectar and sap.  Caterpillars chew; butterflies and moths sip. 

Rules of thumb for telling them apart are that (generally) butterflies sit with their wings held out to the side or folded vertically above their bodies, and moths hold their wings flat over or wrapped around their body.  Butterflies have a thickened tip/knob on the end of their antennae; moths’ antennae may be bare or feathery but are never knobbed.  Butterflies are active by day (though the BugLady had night-feeding Northern Pearly-eye butterflies who hadn’t read that part of the playbook), and moths are generally active in late afternoon and through the night.  Some moths have bright colors and patterns, but as a group, they tend to be drab – what birders call “LBJ’s” – “Little Brown Jobs.”  Because of their pigmented and/or prismatic scales, many butterflies are the definition of the word “dazzling.” 

Buckeyes belong to the “Brush-footed butterfly” family Nymphalidae, a large group of strong, colorful fliers whose front legs are noticeably hairy and are reduced in size (leading to another nickname – “four-footed butterflies”).  There are a number of brush-foots that migrate and others that, contrary to the usual insect practice, overwinter as adults.  Many Nymphalid caterpillars are nocturnal and spiny.  

The “Butterflies of Massachusetts” website says of this beautiful butterfly that “The Halloween-costumed Buckeye wears the colors of fall in New England.”  Buckeyes are named for the eyespots on their wings, which are reminiscent of the spots on buckeye nuts.  Many members of the genus Junonia have eyespots to scare away predators, and an eyespot can even be seen in the Buckeye’s pupal wing case. 

Both the caterpillar and the adult are variable in color – an adult whose underwing surface is tan is from an early summer generation, and one whose underwing is rosy is from the final brood of the year – the color change is controlled by genes and is a response to the temperatures that the caterpillar is exposed to.  There is no other butterfly species in Wisconsin that can be mistaken for them. 

Buckeyes are sun-lovers, butterflies of sunny habitats like open fields, disturbed areas, trails, edges, and grassy dunes, where they often perch on the ground.  “Butterflies of Massachusetts” speculates that this species has become more common since the European settlers cleared the great forests for agriculture, and notes that it is one of our native butterflies that has adopted a non-native “weed” (English plantain) as a food plant.  Adults sip nectar from dogbanes and from those confusing fall composites (asters and goldenrods), and they sip fluids from decaying fruit. 

Males are feisty and territorial, chasing other flying objects, both butterfly and non-butterfly alike.  He scouts for females from a perch on the ground or on low vegetation.  After mating, females oviposit on leaves and leaf buds of host plants – mostly members of the plantain (the lawn plant, not the banana relative) and snapdragon families.  Caterpillars https://bugguide.net/node/view/1939097/bgimage are solitary and non-aggressive, even when they bump into another caterpillar on the same plant.  The pupae https://bugguide.net/node/view/2214613/bgimage are said to look like bird poop (pretty fancy bird poop, indeed!). 

Caterpillar food plants often contain toxic chemicals (iridoid glycosides) that besides being very bitter, will literally stunt the growth of a predator that eats a caterpillar – chemicals that, conversely, make the caterpillars hungry.  Chemicals that, when the female senses them, will stimulate her to oviposit.  Predators seem to sense the presence of the glycosides and prefer caterpillars with low/no levels of them.  Caterpillars must be careful of getting too much of a good thing – excessive amounts of iridoid glycosides can affect their immune system negatively.

Ain’t Nature Grand!

Kate Redmond, The BugLady

Bug of the Week archives:
http://uwm.edu/field-station/category/bug-of-the-week/