elm calligrapha

not listed

not listed

not listed

Elm calligrapha is a medium-sized, once common but now declining, calligrapher beetle. It is historically a species specialist, feeding almost exclusively on American elm. As that species is decimated by Dutch Elm Disease, the beetle moves to alternate hosts, including slippery elm and willow, and possibly dogwood and paper birch.

Adults are 5⁄16″ to ⅜″ (7.5 to 9.5 mm) in length. The body is elongated-oval when viewed from above and very convex when viewed from the side. It is mostly creamy white with dark markings. The head, exoskeletal plate covering the thorax (pronotum), and dark markings on the hardened wing covers (elytra) are black with a metallic green sheen.

The head is dark and is usually partially visible when viewed from above, but it can be withdrawn into the body. The antennae are short, less than half as long as the body. They are weakly clubbed (clavate), gradually enlarged as they approach the tip. The eyes are not notched.

The pronotum is dark and unmarked. It is three times wider than long, nearly as wide as the base of the elytra. The small triangular plate between the bases of the elytra (scutellum) is dark.

The elytra are creamy white with dark markings. The markings are somewhat variable. On each elytron there are 10 to 14 small isolated spots, a boot-shaped spot near the base, and a central stripe. The stripe is connected to four nearby spots, creating four extended lobes, including one at the tip of the elytron.

The legs are brownish-orange. The last part of each leg (tarsus), corresponding to the foot, has five segments. The fourth segment is very short and is concealed within the broadened tip of the third segment, making the tarsus appear to have only four segments. There is a pair of claws at the tip of the tarsus on each leg. The claws are well separated at the base.

5⁄16″ to ⅜″ (7.5 to 9.5 mm)

Elm calligrapha is historically a species specialist, feeding almost exclusively on American elm. As that species is decimated by Dutch Elm Disease, the beetle moves to alternate hosts, including slippery elm and willow, and possibly dogwood and paper birch.

Two generations per year: mid-June to late July and September to October.

Adults chew holes in leaves. Larvae consume the entire leaf except for the veins.

Elm calligrapha is parthenogenetic, meaning that it reproduces asexually. The egg develops without fertilization by sperm. In 1966, a population in Kansas contained only females and their reproduction produced only females. Though highly unusual among leaf beetles (family Chrysomelidae), several Calligrapha species are parthenogenetic.

Adults of the second generation overwinter in a sheltered bark crevice at the base of a tree or in topsoil. They emerge in late May or early April and resume feeding.

Leaves of mostly American elm, sometimes also slippery elm and willow, possibly also dogwood and paper birch.

Leaves of mostly American elm, sometimes also slippery elm and willow, possibly also dogwood and paper birch.

Sources

27, 29, 30, 82, 83.

New distribution records and biogeography of Calligrapha species in North America (Coleoptera: Chrysomelidae, Chrysomelinae) By Gómez-Zurita J. Canadian Field-Naturalist 119: 88-100, 2005.

Common (CCESR)

There are no records of this beetle in Minnesota except at Cedar Creek Ecosystem Science Reserve, where it is listed as common. Its numbers are declining as its hosts succumb to Dutch Elm Disease.

Tribe
Some sources place the genus Calligrapha in the tribe Chrysomelini, others sources place it in the tribe Doryphorini.

Species group
The species Calligrapha scalaris was first described by John Eatton LeConte in 1824 on the basis of color and two conspicuous markings on the wing covers (elytra): a moon-shaped marking in the shoulder (humeral) area; and a broad, tooth-like marking connected to the middle (sutural) stripe. The beetle was reported to be an occasional serious pest of American elm. LeConte’s description accurately distinguished the new species from all other Calligrapha species then known. Since then, at least thirteen new species have been described that share these characters.

In 1945, W. J. Brown identified a species complex of several species that were morphologically very similar but had very different host preferences and ecologies. A more recent study (Gómez-Zurita J., 2015) analyzed the original material from the Calligrapha scalaris collections of LeConte (1824) and of G. H. Horn (1884). The author found the collections contained as many as nine distinct species, many having no association with elm. He redefined the original species and defined fourteen species as the “Calligrapha scalaris” group.