Tragidion annulatum LeConte

Swift, Ian & Ray, Ann M., 2008, A review of the genus Tragidion Audinet-Serville, 1834 (Coleoptera: Cerambycidae: Cerambycinae: Trachyderini), Zootaxa 1892, pp. 1-25 : 10-13

Tragidion annulatum LeConte

( Figs 1 C–D, 7C)

Tragidion annulatum LeConte, 1858: 83 ; Leng, 1886:81. Type locality: Sonora, Mexico (probably an error). Tragidion annulatum var. peninsulare Schaeffer, 1908:339 ; Casey, 1912: 321. Type locality: San Felipe, Baja California, Mexico. New synonymy.

Tragidion peninsulare peninsulare: Linsley, 1940: 137 ; Linsley, 1942: 60; Hovore, 1988:28 Tragidion peninsulare californicum Linsley, 1940: 137 . Type locality: Paradise Valley, Kings River, Kern County, California, USA. New synonymy.

Material examined: 49 specimens, including one lectotype and two paralectotypes at MCZC.

Diagnosis. Tragidion annulatum is fairly distinctive within the genus. It most closely resembles T. deceptum . From T. deceptum , it can be distinguished by the elytral costae which extend to the apex; the dark basal elytral band which is very narrow and does not exceed the scutellum; and the distinctive bright metallic blue reflections of the pubescence on the venter and metatibia. Linsley (1940, 1942, 1962) had difficulty interpreting T. annulatum , and incorrectly assigned other names to the California populations. The incorrect type locality may have added to his confusion (see below). In Linsley’s treatment (1962), T. annulatum is listed as occurring in the lowland deserts of the southwest. Tragidion annulatum , however, is common along the western coast of North America , inhabiting deserts only in the Baja Peninsula.

Based on an examination of all available specimens, the primary characters used to separate Linsley’s californicum subspecies from the nominate form – smaller size and narrower tarsi – are entirely clinal and allometric, as the overall size of specimens decreases farther north. Therefore, material from northern Baja California, Mexico and California, USA are considered to represent T. annulatum .

Discussion. The International Code of Zoological Nomenclature (ICZN, 1999) in Article 74.7.3 specifically states that designations of lectotypes after 1999 must “contain an express statement of the taxonomic purpose of the designation”. The lectotype designation herein for T. annulatum is to assign a single specimen of this species as the sole name-bearing specimen to stabilize future nomenclature. There are three specimens labeled as T. annulatum LeConte in the MCZC, none of which is designated as a type. Therefore, a representative was selected, and a label stating “ LECTOTYPE Tragidion annulatum LeConte Ian Swift, 2008 ” was affixed to that specimen.

LeConte (1858) lists “Sonora, Mexico ” as the type locality for this species. However, of the 49 specimens examined for this study, we have not seen any T. annulatum from Sonora or anywhere in mainland Mexico. While it may be possible that this species occurs in that region, the type series matches very closely specimens from southern Baja California Sur, Mexico, and this is likely where the type series was collected. Therefore, under recommendation 76A.2 of the ICZN, the type locality listed for this species is considered an error, and should be amended to indicate Baja California Sur, Mexico.

Distribution ( Fig. 7 C). Throughout the western coast of North America including California, USA, and the states of Baja California, and Baja California Sur, Mexico. This species occurs in a wide variety of habitats, including Sonoran Desert in the Baja Peninsula, and in tropical deciduous forest and montane oak woodland in the cape region. In California, it is found in many different habitats, including chaparral, oak, and conifer woodlands.

Ecology. Linsley (1962) and Hovore and Giesbert (1976) summarized the ecology of this species in part. Individuals of T. annulatum are strongly attracted to brushfires and burning vegetation ( Hovore and Giesbert 1976). Adults have been observed flying into more than 25 brushfires throughout the southern California region from 1994–2007, and the larval workings have been observed at most other burned sites (pers. obs.). During some of these brushfires, individuals landed on still-burning and smoldering shrubs, causing their legs and abdomens to melt to the surface of the branches. At several post-burn sites, the melted bodies of this species were common on the charred branches of their hosts. Females have been observed ovipositing on woody shrubs that have been burned. This behavior is generally similar to that of some species in the buprestid genus Melanophila Eschscholtz ( Sowards et al., 2001) . However, Tragidion does not possess infra-red receptors used by Melanophila to locate appropriate host plants (pers. obs.). The means by which T. annulatum detect burning vegetation is unknown. Given the abundance of T. annulatum at burned sites, and the frequency and importance of brushfires in Mediterranean shrublands in California and northern Baja California ( Keeley 2006), T. annulatum is likely an important member of the insect fauna associated with the decomposition of burned woody material. The larval period is one year in all laboratory-reared samples. The larvae mine galleries throughout the branches of their host, pupating in a chamber parallel to the grain.

Figures

FIGURE 1. Dorsal habitus photos of Tragidion spp. A, Tragidion agave (male); B, T. agave (female); C, T. annulatum (male); D, T. annulatum (female); E, T. armatum (male); F, T. armatum (female).

FIGURE 7. Distribution map of Tragidion spp. A, Tragidion agave; B, T. gracilipes; C, T. annulatum; D, T. deceptum; E, T. densiventre; F, T. auripenne.