Taxonomic history

Xyleborus fornicatus Eichhoff, 1868b: 151.

Euwallacea fornicatus (Eichhoff): Wood, 1989: 173.

Synonyms

Xyleborus fornicatus fornicatus Eichhoff, 1868b: Beeson, 1930: 234.

Xyleborus tapatapaoensis Schedl, 1951b: 152. Wood, 1989: 173.

Xyleborus whitfordiodendrus Schedl, 1942a: 189. Wood, 1989: 173; Smith et al., 2019: 6.

Diagnosis

2.6−2.7 mm long (mean = 2.66 mm; n = 5); 2.25−2.36 times as long as wide. This species is distinguished by the pronotum basic (type 2) when viewed dorsally, anterior margin appearing rounded; elytral declivity rounded; declivital face convex; protibia outer margin rounded with 8 or 9 socketed denticles, denticles small, their sockets small; declivital surface shining; interstriae bearing sparse small granules, posterolateral margin costate. This species is nearly identical to E. malloti and E. n. sp. 5 and can be separated by the elytral bases rounded and posterolateral declivital costa carinate and never granulate.

This species is part of the Euwallacea fornicatus species complex, and the most reliable method to ensure accurate identification of these species is through generation of COI barcoding sequences (Gomez et al. 2018b, Smith et al. 2019). Gomez et al. (2018b; figure 1) provide morphological characters for separating the species based on measurements of elytral length (lateral view; diagonally measured from the elytral base to the apex) and pronotal length (lateral view; on a diagonal from pronotal apex to pronotal base). Species can be diagnosed using the combination of measurements given in Smith et al. 2019:

species total length
(dorsal)
length/width ratio
(dorsal)
elytral length
(lateral; diagonal)
pronotal length (lateral; diagonal) elytral width (dorsal) pronotal width (dorsal) protibial
denticles
E. fornicatior 2.20–2.37 2.15−2.35 1.40–1.46 1.02–1.06 0.48–0.52 1.00–1.06 6−7
E. fornicatus 2.60−2.70 2.25−2.36 1.44–1.72 1.02–1.16 0.48–0.62 1.00–1.14 8–9
E. kuroshio 2.40−2.80 2.17−2.40 1.50–1.82 1.08–1.16 0.52–0.56 1.06–1.16 8−11
E. perbrevis 2.30−2.50 2.46−2.55 1.42–1.68 1.04–1.16 0.48–0.56 1.02–1.14 7−10

 

May be confused with

This species is part of the Euwallacea fornicatus species complex along with E. fornicatior, E. kuroshio and E. perbrevis from which it is difficult to distinguish. The species is also similar to Coptodryas inornata, E. andamanensis, E. geminus, E. malloti, E. neptis, E. semirudis, E. testudinatus, E. velatus, and Xylosandrus formosae.

Distribution

China (Chongqing, Guizhou, Hong Kong, Yunnan), India (Uttar Pradesh), Japan (Bonin Islands, Okinawa), Malaysia (Sabah)*, Samoa, Sri Lanka, Taiwan, Thailand, and Vietnam. This species has been introduced into Israel, South Africa, and the United States (California) (cited as PSHB and/or E. whitfordiodendrus) (Smith et al. 2019). Distribution records published prior to 2018 may not reflect the actual species distribution.

Host plants

Polyphagous (Stouthamer et al. 2017). In Samoa, it has been recorded as Xyleborus tapatapoensis from Albizia sp., Bauhinia variegata, Erythrina orientalis (Fabaceae), Ochroma lagopus (Malvaceae), and Milicia (=Chlorophora) excelsa (Moraceae) (Beaver 1976). It has also been recorded from the following hosts under different names: Callerya (Fabaceae), Persea americana (Lauraceae) (O'Donnell et al. 2015, Mendel et al. 2017 as Euwallacea sp. #1 and PSHB respectively), Robinia (Fabaceae) (Haack 2006), Sambucus (Adoxaceae), Liquidambar (Altingiaceae), Schinus (Anacardiaceae), Alnus (Betulaceae), Ricinus (Euphorbiaceae), Acacia (Fabaceae), Carya, Quercus (Fagaceae), Juglans (Juglandaceae), Umbellaria (Lauraceae), Magnolia (Magnoliaceae), Ficus, Morus (Moraceae), Eucalyptus (Myrtaceae), Fraxinus (Oleaceae), Platanus (Platanaceae), Prunus (Rosaceae), Populus, Salix (Salicaceae), Acer (Sapindaceae), Ailanthus (Simaroubaceae), and Ulmus (Ulmaceae) (Mendel et al. 2017, Coleman et al. 2019 as PSHB). It is also recorded from Cunninghamia (Cupressaceae), and Erythrina (Fabaceae) (Smith et al. 2019).

Remarks

This species is commonly known as the polyphagous shot hole borer (PSHB) and has been referred to as this in numerous publications before the species was formally recognized as E. whitfordiodendrus (e.g. Cooperband et al. 2016, Stouthamer et al. 2017, Gomez et al. 2018b, Papp et al. 2018) and later as E. fornicatus (Smith et al. 2019).

This species has recently been the subject of intensive study which revealed that the species is comprised of four sibling species, nearly indistinguishable morphologically, but represent separate lineages using molecular data and are associated with different species of ambrosia fungi (Eskalen et al. 2013, Freeman et al. 2013, O'Donnell et al. 2015, Chen et al. 2016, Cooperband et al. 2016, Stouthamer et al. 2017, Gomez et al. 2018b). The species limits were recently revised by Gomez et al. (2018b) and Smith et al. (2019).

DNA data

Sequences are available for COI and CAD. Additional COI sequences can be found in Smith et al. 2019.

COI: MN266858MN266859MN266860MN266861

CAD: MN620230MN620231MN620232MN620233