The lectotype of Longitarsus californicus (Motschulsky, 1845) is designated, described, and illustrated. An illustrated key to eight light-colored Longitarsus species known to occur in the western United States is presented. A brief history of Russian entomological collecting in North America during the first half of 19^th century, with specimens preserved in Zoological Museum of Moscow University, Moscow and Zoological Institute, St. Petersburg, is provided.

America north of Mexico, Il’ya Gavrilovich Voznesensky, Johann Friedrich Gustav von Eschscholtz, key for identification, leaf beetles

Longitarsus Latreille, 1829 is the most species-rich genus among flea beetles, with more than 700 species worldwide (Konstantinov unpublished compilation). Fifty-one valid species of Longitarsus are known to occur in America north of Mexico (Riley et al. 2003; Konstantinov unpublished compilation). Thirty-nine of them are native, and 12 are introduced, either as biological control agents of invasive weeds or unintentionally (LeSage 1988; Pentinsaari et al. 2019). North American Longitarsus has never been reviewed or revised. The most recent available key for species identification is that of Horn (1889). A few regional keys were later published, which included Longitarsus (e.g. Beller and Hatch 1932; Wilcox 1954; Balsbaugh and Hays 1972). Most North American Longitarsus species were described by Blatchley (1923), Horn (1889), and LeConte (1859), and their type specimens are available for study at major Canadian and United States entomological collections (Canadian National Collection, Ottawa, Ontario; Museum of Comparative Zoology, Cambridge, Massachusetts; Purdue Entomological Research Collection, West Lafayette, Indiana; and National Museum of Natural History, Washington DC). However, the whereabouts of the type specimen and, therefore, the certain identity of one species, Longitarsus californicus (Motschulsky, 1845), has remained a mystery until recently, when a single female specimen was discovered by VYS in one of the drawers of the Motschulsky collection in the Zoological Museum of Moscow University, Moscow, Russia (ZMUM). The Motschulsky beetle collection contains approximately 60,000 specimens, of which about 4,000 are types (Lyubarsky 2009). Most of the types have been recognized as such and transferred from the main holdings to special drawers. However, beetle types previously considered missing are still being discovered in the main holdings of Motschulsky collection (Savitsky 2018). The Longitarsus californicus specimen was pinned on a short pin with a small label in such a way that the specimen was close to the bottom of the drawer and was not recognized as the type by previous ZMUM curators.

The origin of the specimen and its exact collecting locality remain unknown. It could not have come from Motschulsky’s own collecting in the United States, which he visited in 1853–1854, nearly 10 years after the description of L. californicus was published. In a letter to Édouard Ménétries dated July 15, 1854, Motschulsky mentioned a visit to the LeConte collection which contained “very different things than what Dr. Voznesensky brought” from California (Motschulsky 2013). Indeed, there is a slight possibility that the specimen of L. californicus came from Il’ya Gavrilovich Voznesensky (1816–1871), who travelled to western North America in 1839–1849 (Gnucheva 1940), where he visited Fort Ross, Drake’s Cape, San Francisco Bay, Fort Ross at Bodega Bay, Mount St. Helens, and Khlebnikov Valley. Each location originally had its own color-coded label (Feklova 2014). However, Motschulsky often replaced original labels with his own (Koponen and Niemelä 2020), so the color of the L. californicus label cannot help in identifying its type locality. The bulk of the Voznesensky zoological collection was transferred to the Zoological Institute (St. Petersburg, Russia) most likely around 1849 (Feklova 2014).

The other likely source of California specimens described by Motschulsky in 1845 is collection of Johann Friedrich Gustav von Eschscholtz (1793–1831), an early pioneer in the western North American coleopterology. He was the naturalist in two expeditions in 1815–1817 and 1823–1826 to the western United States (Koponen and Niemelä 2020). Beetles are well represented among large biological collections that he made. New beetle genera and species were described by Eschscholtz (1829–1833) and Mannerheim (1843) based on North American specimens collected by Eschscholtz. Eschscholtz’s collection was transferred to the Zoological Museum of Moscow University in the summer of 1837 (Lyubarsky 2009) at a time of Motschulsky’s affiliation with the museum and well before 1845 (Koponen and Niemelä 2020).

The source of the flea beetle diversity is an unpublished compilation of flea beetle genera and species of the world, which is a FileMakerPro database maintained by ASK since 2006. It is cited as “Konstantinov unpublished compilation”. The lectotype of L. californicus was processed as follows. The abdomen, genitalia and terminalia were studied at magnifications up to ×400 (spermatheca) and documented from glycerol preparations, using a Micromed-3 microscope equipped with a ToupCam 9.0 MP digital eyepiece camera. The other photographs were taken using a Canon EOS 5D Mark IV camera with a Canon MP-E 65 mm objective lens. The USNM specimen of L. californicus was photographed with Macropod Pro photomacrography system (Macroscopic Solutions, LLC, Tolland, CT, USA) and processed with Zerene Stacker v. 1.04 and edited with Adobe Photoshop Elements 2020. Dissecting techniques and morphological terminology follow Konstantinov (1998). Numbering only visible tarsomeres and abdominal segmentation justified previously (Konstantinov et al. 2022). The type locality is cited verbatim as it appears in the original description.

Specimens studied in this paper are deposited in the following collections:

USMN National Museum of Natural History, Washington DC, USA.

ZMUM Zoological Museum of Moscow University, Moscow, Russia.

In addition to the female lectotype, we studied three other specimens, two females and one male, identified as L. californicus (USNM). The identification label for these does not have the name of the identifier, and we could not recognize the handwriting, so we do not know who made that identification. The identification label lists Horn as the author of the species; however, we could not find any Longitarsus named californicus by Horn. Dissection of one female revealed that the genitalia, especially the spermatheca and vaginal palpi, are very similar to those of the lectotype of L. californicus. The tignum of the lectotype (Fig. 14) is slightly different from that of the USNM specimen (Fig. 22) in having a narrower anterior part. In other features, the lectotype and female USNM specimens are very similar. Therefore, we confirm the identification of the three USNM specimens, including the male, as L. californicus.

Eight yellow Longitarsus species are known to occur in the western United States, as delimited by Lingafelter (2007) and Yanega (1996). Two species, L. jacobaeae Waterhouse and L. flavicornis Stephens, were introduced into North America (LeSage 1988). As shown in previous studies, Longitarsus species may be sorted into species groups based on the general shape of their median lobe of aedeagi (Konstantinov and Dorr 2023; Liang et al. 2023). Longitarsus californicus is clearly close to L. livens LeConte and L. vanus Horn in having the median lobe nearly straight in lateral view and with only a slightly S-shaped apex. In ventral view, the lobe is nearly parallel-sided but slightly narrower in the middle. The apex is gradually narrowing and without a well-differentiated denticle. The membranous window is narrow and constricted towards base but not reaching it (Fig. 23). Longitarsus californicus can be separated from these and other light-colored Longitarsus species known to occur in western United States using the following key.

We are grateful to Maurizio Biondi (University of L’Aquila, L’Aquila, Italy) and Michael Schmitt (Universität Greifswald, Greifswald, Germany), who kindly provided valuable comments on an earlier version of the manuscript.

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