Bug of the Week – Red Admiral Butterfly

Salutations BugFans,

Red admiral butterflies hold a special place in the BugLady’s heart (along with the “ickybug” of recent BOTW fame); Red Admirals were an important “entry level” bug during the BugLady’s childhood (more about that in a sec).   This is a complete overhaul of a way-too-short episode that appeared in October of 2008.

red admiral15 3rz
Red Admirals (Vanessa atalanta)
Red admiral
Red admiral

Red Admirals (Vanessa atalanta) belong to the largest butterfly family, the Nymphalidae or Brush-footed butterflies. Their antennae are very “knobbed,” and their two front legs are covered with bristles and reduced in size (so they have, effectively, only two pairs of walking legs). There are two broods of RAs per summer in most of the north, and there are two “forms” – a slightly smaller and less flashy winter form and a larger, more intensely-colored summer form.

They are strong, fast, somewhat erratic flyers with a wingspread of two inches, plus-or-minus, and distinctly-colored upper wing surfaces, but an RA that’s sitting with its wings folded is pretty well camouflaged. At a quick glance, the only butterflies that might be mistaken for a Red Admiral are (possibly) the Painted Lady, and the Milbert’s Tortoiseshell, a butterfly noted for population swings, but one that has been absent from the BugLady’s vistas for so long that she doesn’t even have a digital picture of one https://wisconsinbutterflies.org/butterfly/species/89-milberts-tortoiseshell.

Painted lady
Painted lady

RAs have population eruptions and they wander (and nobody really knows why), and so, to varying degrees, do the other Vanessas – the Painted Lady, American Lady, and the West Coast Lady. The Painted Lady (of previous BOTW fame) is said to be the most widely distributed butterfly globally and is found in temperate regions of four continents plus Central America (and scientists do think they know why Painted Lady’s roam). The American Lady is considered “somewhat migratory,” and as its name suggests, the West Coast Lady is found from the Pacific through eastern Colorado.

American lady
American lady

The RA’s range is only a little smaller than the Painted Lady’s, and within that range it’s found in many habitats – suburbs, parks, gardens, wooded edges and trails, around wetlands, bottomlands, damp fields, and ditches – anywhere it can be close to the various species of nettles that are its caterpillar’s food plants. Most sources restrict the caterpillars to nettles, but a few add to the list thistles, willows, and/or members of the plant family Cannabaceae (yes, that plant family), a family that, the BugLady was surprised to discover, is primarily made up of hackberries and hops. Adults are seen nectaring on flowers, but they prefer non-floral calories from fermenting fruit, animal scat, and sap oozes on tree trunks.

Males are said to defend territories in clearings and semi-sunny edges in the late afternoon and to scout for females from perches that they revisit. The subject of whether the males are truly territorial or simply chase everything until they determine its species and gender is somewhat up in the air (butterfly eyesight – not 20:20). Intruders get chased upwards in a spiral and out over the treetops. Find a technical discussion of territorial behavior at http://lepidopteraresearchfoundation.org/journals/18/PDF18/18-036.pdf.

Females fly slowly and purposefully in search of host plants.

Butterflies scratch a leaf’s surface with raspy spots at the bottom of their tarsi and then sample (smell/sense/taste) the chemistry. If the RA recognizes it, she will lay an egg on the top surface of a host plant leaf. A caterpillar http://bugguide.net/node/view/1039554/bgimage folds a leaf around itself and shelters inside, leaving the leaf to feed or to form a larger tent. The larval stage lasts about a month; the caterpillar makes a pupal case by sewing several leaves together and hanging inside it, head down http://bugguide.net/node/view/654244/bgimage

(pictures of all stages are at http://entnemdept.ufl.edu/creatures/bfly/red_admiral.htm).

Wandering RAs started showing up in numbers in the second week in May (along with some Painted Ladies), but, well, there’s some question about that, too. In the more southerly parts of their range, both adults and pupae hibernate. Ebner, in Butterflies of Wisconsin (1970) says that,” a few individuals may overwinter as adults in Wisconsin, emerging in the balmy days of late April and May.” RAs are known to overwinter as adults as far north as New York. Whether they are newly-awakened or newly-arrived, our April-May RAs initiate the two broods. Brood #1, the larger, showier summer brood will be coming out by the start of July. They produce the winter form, seen from late August through the first frosts. From what the BugLady reads, the winter crew is non-reproductive (like the Gen. 5 Monarch butterflies) and they pack away fat reserves that allow them to migrate or to hibernate. Whatever their winter strategy, they become reproductively mature the following spring.

This was the Bug Lady’s natal butterfly – her favorite insect as a kid. If she stood for a while on the lawn, a red admiral would fly over and sit on her out-stretched hand and sometimes eat a little salty sweat as she admired it.

One older source says that butterflies and moths void a drop of liquid (red, in some species) soon after leaving their pupal cases. They sometimes do this while airborne, and when large numbers of butterflies emerged simultaneously, the phenomenon, called “Red Rain” was, in ancient times and is still today, the subject of wild religious fear, superstition, repentance and/or massacre.

As always, the BugLady recommends Door 3, repentance.

Kate Redmond, The BugLady

And, on a dragonfly note – if you see a milky strand at the water’s surface in a wetland near you, and if you’re lucky, it could be the egg strand of a baskettail dragonfly.

Baskettail eggs
Baskettail eggs

Bug of the Week archives:

http://www4.uwm.edu/fieldstation/naturalhistory/bugoftheweek/

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