Psenulus fuscipennis, copyright Rafael Carbonell Font.

Belongs within: Psenini.

Psenulus: silk-weaving wasps
Published 28 July 2014
Female Psenulus pallipes carrying an aphid back to her nest, copyright Jeremy Early.

Because I am an obsessive-compulsive weirdo, I spend a good chunk of my spare time at home sorting through biology publications and pulling out names. Back on July 1, I tweeted: “And from tonight, I delve into sphecoids. To species level. This could take even longer than the oribatids.” Never, as it turns out, were truer words spoken, as we have now very nearly reached the end of July, and I am still only a relatively small part of the way through this diverse group of wasps (to be more specific, I’ve been taking stuff out of Bohart & Menke’s [1976] Sphecid Wasps of the World, and I’ve only gotten as far as p. 179 of what is a 695-page book: there are over 7500 species listed in that book, a depressing high proportion of which appear to have originally been placed in the genus Sphex). And seeing as so much of my time recently has been spent on sphecoids, it is only appropriate that my semi-random selection for this week’s post has been one: the pemphredonine Psenulus trisulcus.

The sphecoids are a group of solitary wasps including such beasts as the digger wasps and sand wasps. Bohart & Menke (1976) placed them all in a single family Sphecidae, but this does not represent a monophyletic group, as some ‘sphecoids’ are more closely related to bees than to other sphecoids. As a result, most recent authors have divided the sphecoids between three families: the Ampulicidae (cockroach wasps), Sphecidae (digger wasps, etc.) and Crabronidae (sand wasps, etc.) The Pemphredoninae are a group of mostly quite small wasps in the last of these families. Psenulus is a genus of about 120 species of pemphredonines found on most continents except South America; P. trisulcus is one of only a small number of Psenulus species found in North America (the genus is most diverse in the Oriental region). Like other sphecoids, females of Psenulus species provision their nests with paralysed prey insects for their larvae to feed on after hatching. While more familiar sphecoids such as digger or sand wasps may dig tunnels in which to construct their nest cells, Psenulus species use hollows such as beetle borings in plant stems. Krombein (1979) listed P. trisulcus as nesting in elder stems; another Psenulus species has been recorded constructing cells in hollow grass stems floating on water (Bohart & Menke 1976). I have not been able to find a record of the preferred prey of P. trisulcus itself, but closely related species such as P. pallipes, a Holarctic species shown in the photo at the top of this post, attack aphids. In the case of P. pallipes, a single nest cell may be packed with as many as 27 aphids, providing plenty of food for an emerging larva. Other Psenulus species may collect other Hemiptera, such as psyllids (plant-lice) or leafhoppers. Psenulus trisulcus resembles P. pallipes in its overall black coloration, and the characters distinguishing the two would not be visible without a close microscopic examination: in P. trisulcus, the ridge running between the antennae is marked by longitudinal grooves that are not present in P. pallipes, and the petiole of P. trisulcus has a ridge along its underside (Malloch 1933*).

*As corrected by Pate (1944), who noted that Malloch’s “trisulcus” was actually a different species that he named “parenosas” (subsequently regarded as a subspecies of pallipes), and that the true trisulcus was actually Malloch’s “sulcatus“.

Pinned specimen of Psenulus trisulcus, copyright York University.

The nests of Psenulus trisulcus and P. pallipes are also unusual in being lined with silk, with silk also being used to construct the partitions between cells. While many insects produce silk as larvae, it is more uncommon for them to continue doing so as adults (and only the females do so in the case of Psenulus). The source of Psenulus‘ silk was long uncertain (with one researcher suggesting that it was extruded from the labial palps), until Melo (1997) established that it was secreted from bristle-like spinnerets that form fringes on the hind margins of the fourth and fifth sternites of the gaster. However, not all Psenulus species have such fringes: Melo (1997) examined three spinneret-less species and found that their silk glands opened directly on the underside of the gaster (with long erect setae possibly assisting in the spreading of silk in these species). This makes for an interesting comparison with spiders, in which the fossil Attercopus suggests the evolution of spinnerets from previously disassociated silk glands. Unfortunately, we don’t yet really know what the relationships are within Psenulus, and whether the spinneret-less model is truly ancestral.

Systematics of Psenulus
Psenulus Kohl 1896 (see below for synonymy)BM76
|--*P. fuscipennis (Dahlbom 1843) (see below for synonymy)BM76
| |--P. f. fuscipennisBM76
| `--P. f. japonicus Tsuneki 1959BM76
|--P. ajaxellus (Rohwer 1923) [=Diodontus ajaxellus]BM76
|--P. alboscutellatus Arnold 1945BM76
|--P. alienus (Krombein 1950) [=Diodontus alienus]BM76
|--P. alveolatus van Lith 1974BM76
|--P. annamensis van Lith 1972BM76
|--P. anomoneurae (Yasumatsu 1938) [=*Nipponopsen anomoneurae; incl. P. mandibularis Tsuneki 1959]BM76
|--P. araucarius van Lith 1972BM76
|--P. aurifasciatus van Lith 1974BM76
|--P. avernus Leclercq 1961BM76
|--P. bakeri (Rohwer 1921) [=Diodontus bakeri]BM76
| |--P. b. bakeriBM76
| |--P. b. boholensis van Lith 1962BM76
| `--P. b. canlaoensis van Lith 1962BM76
|--P. baltazarae van Lith 1962BM76
| |--P. b. baltazaraeBM76
| `--P. b. luteus van Lith 1962BM76
|--P. bengalensis van Lith 1972BM76
|--P. benoiti Leclerc1 1961BM76
|--P. berlandi Beaumont 1937 [incl. Psen haemorrhoidalis Berland 1925 non Costa 1871]BM76
|--P. bicinctus Turner 1912BM76
|--P. bidentatus (Cameron 1910) [=Psen bidentatus; incl. Psenulus rubrocaudatus Turner 1912]BM76
| |--P. b. bidentatusBM76
| `--P. b. pallidus van Lith 1974BM76
|--P. birganjensis van Lith 1973BM76
|--P. bisicatus van Lith 1972BM76
|--P. capensis Brauns 1899 [incl. P. laevior Arnold 1951, P. pauxillus Arnold 1947]BM76
| |--P. c. capensisBM76
| |--P. c. basilewskyi Leclercq 1955BM76
| `--P. c. latiannulatus Cameron 1910BM76
|--P. carinifrons (Cameron 1902) [=Psen carinifrons]BM76
| |--P. c. carinifronsBM76
| |--P. c. bismarkensis van Lith 1970BM76
| |--P. c. iwatai Gussakovskij 1934 1934 [=*Eopsenulus iwatai]BM76
| |--P. c. malayanus van Lith 1969BM76
| |--P. c. rohweri van Lith 1962BM76
| `--P. c. scutellatus Turner 1912 [incl. P. extremus van Lith 1966]BM76
|--P. cavifrons van Lith 1962BM76
|--P. ceylonicus van Lith 1972BM76
|--P. chariis van Lith 1972BM76
|--P. chillcotti van Lith 1973BM76
|--P. compactus van Lith 1962BM76
|--P. concolor (Dahlbom 1843) [=Psen concolor; incl. Psen ambiguus Schenck 1857, Psen intermedius Schenck 1857]BM76
|--P. continentis van Lith 1962BM76
|--P. corporali van Lith 1962BM76
|--P. crabroniformis (Smith 1858) [=Mellinus crabroniformis]BM76
| |--P. c. crabroniformisBM76
| `--P. c. sumatranus (Ritsema 1880) [=Psen sumatranus]BM76
|--P. cypriacus van Lith 1973BM76
|--P. decipiens van Lith 1976TB20
|--P. dentatus van Lith 1962BM76
|--P. dilectus (Saussure 1892) [=Psen dilectus, *Stenomellinus dilectus]BM76
|--P. diversus van Lith 1962BM76
|--P. ealae Leclercq 1961BM76
|--P. elegans van Lith 1962BM76
|--P. ephippius Taylor, Barthélémy et al. 2020TB20
|--P. erraticus (Smith 1861) [=Psen erraticus]BM76
| |--P. e. erraticusBM76
| |--P. e. basilanensis (Rohwer 1921) [=Diodontus basilanensis]BM76
| `--P. e. butuanensis van Lith 1962BM76
|--P. erusus Leclercq 1961BM76
|--P. esuchus (Rohwer 1923) [=Diodontus esuchus]BM76
|--P. filicornis (Rohwer 1923) [=Diodontus filicornis]BM76
|--P. formosicola Strand 1915BM76
|--P. freetownensis van Lith 1974BM76
|--P. frontalis (Fox 1898) (see below for synonymy)BM76
|--P. fulgidus Arnold 1945BM76
|--P. fulvicornis (Schenck 1857) [=Psen fulvicornis]BM76
|--P. fuscipes Tsuneki 1959BM76
|--P. garambae Leclercq 1961BM76
|--P. ghesquierei Leclercq 1961BM76
|--P. gibbus Taylor, Barthélémy et al. 2020TB20
|--P. godavariensis van Lith 1973BM76
|--P. hemicyclius van Lith 1962BM76
|--P. hoozanius van Lith 1972BM76
|--P. impressus van Lith 1976TB20
|--P. interstitialis Cameron 1906 [incl. Psen lutescens Turner 1907]BM76
| |--P. i. interstitialisBM76
| |--P. i. baliensis van Lith 1962BM76
| |--P. i. davanus (Rohwer 1923) [=Diodontus davanus]BM76
| |--P. i. luzonensis (Rohwer 1921) [=Diodontus luzonensis]BM76
| |--P. i. pseudolineatus van Lith 1962BM76
| `--P. i. solomonensis van Lith 1972BM76
|--P. jacoti van Lith 1974BM76
|--P. jalapensis Bohart & Grissell 1969BM76
|--P. kohli Arnold 1923BM76
|--P. laevigatus (Schenck 1857) [=Psen laevigatus; incl. Psen distinctus Chevrier 1870]BM76
|--P. laevis Gussakovskij 1928BM76
|--P. lamprus van Lith 1972BM76
|--P. leoninus van Lith 1974BM76
|--P. lubricus (Pérez 1902) [=Psen lubricus]BM76
|--P. luctuosus Arnold 1929BM76
|--P. lusingae Leclercq 1961BM76
|--P. luteopictus (Rohwer 1921) [=Diodontus luteopictus]BM76
| |--P. l. luteopictusBM76
| `--P. l. calapanensis van Lith 1962BM76
|--P. maai van Lith 1967BM76
|--P. macrodentatus van Lith 1962BM76
|--P. maculatus van Lith 1962BM76
| |--P. m. maculatusBM76
| `--P. m. javanensis van Lith 1962BM76
|--P. maculipes Tsuneki 1959BM76
|--P. mauritii van Lith 1969BM76
|--P. maurus (Rohwer 1921) [=Diodontus maurus]BM76
|--P. melanonotus van Lith 1969BM76
|--P. meridionalis Beaumont 1937BM76
|--P. ‘montanus’ (Cameron 1907) [=Psen montanus non Costa 1868]BM76
|--P. multipictus (Rohwer 1921) [=Diodontus multipictus]BM76
|--P. nasicornis van Lith 1972BM76
|--P. neptunus van Lith 1972BM76
|--P. nietneri van Lith 1972BM76
|--P. nigeriae Leclercq 1961BM76
|--P. nigrolineatus (Cameron 1907) [=Mellinus nigrolineatus]BM76
| |--P. n. nigrolineatusBM76
| |--P. n. ajax (Rohwer 1921) [=Diodontus ajax]BM76
| |--P. n. dubius van Lith 1962BM76
| |--P. n. flavicornis van Lith 1962BM76
| `--P. n. sulphureus van Lith 1962BM76
|--P. nigromaculatus (Cameron 1907) [=Mellinus nigromaculatus]BM76
|--P. nikkoensis Tsuneki 1959BM76
|--P. nipponensis Yasumatsu 1942BM76
|--P. noonadanius van Lith 1970BM76
|--P. orinus van Lith 1973BM76
|--P. ornatus (Ritsema 1876) [=Psen ornatus]BM76
| |--P. o. ornatusBM76
| |--P. o. kankauensis Strand 1915BM76
| |--P. o. pempuchiensis Tsuneki 1971BM76
| `--P. o. tritis van Lith 1962BM76
|--P. oweni van Lith 1974BM76
|--P. pagdeni van Lith 1962BM76
|--P. pallens Taylor, Barthélémy et al. 2020TB20
|--P. pallidicollis van Lith 1972BM76
|--P. pallipes (Panzer 1798)BM76 (see below for synonymy)
| |--P. p. pallipesBM76
| |--P. p. chevrieri (Tournier 1889) [=Psen chevrieri]BM76
| |--P. p. parenosas (Pate 1944) [=Diodontus parenosas]BM76
| |--P. p. pygmaeus (Tournier 1889) [=Psen pygmaeus]BM76
| `--P. p. yamatonis Tsuneki 1959BM76
|--P. pan Beaumont 1967BM76
|--P. parvidentatus van Lith 1972BM76
|--P. pateiR54
|--P. paulisae Leclercq 1961BM76
|--P. penangensis (Rohwer 1923) [=Diodontus penangensis]BM76
|--P. pendleburyi van Lith 1962BM76
|--P. peterseni van Lith 1970BM76
|--P. philippinensis (Rohwer 1921) [=Diodontus philippinensis]BM76
| |--P. p. philippinensisBM76
| `--P. p. dapitanensis (Rohwer 1923) [=Diodontus dapitanensis]BM76
|--P. pseudajax van Lith 1962BM76
| |--P. p. pseudajaxBM76
| `--P. p. holtmanni van Lith 1972BM76
|--P. pulcherrimus (Bingham 1896) [=Psen pulcherrimus]BM76
| |--P. p. pulcherrimusBM76
| |--P. p. eburneus van Lith 1969BM76
| `--P. p. projectus van Lith 1962BM76
|--P. puncticeps (Cameron 1907) (see below for synonymy)BM76
|--P. quadridentatus van Lith 1962BM76
| |--P. q. quadridentatusBM76
| `--P. q. formosanus Tsuneki 1966BM76
|--P. reticulosus Arnold 1945BM76
|--P. rufobalteatus (Cameron 1904) [=Psen rufobalteatus]BM76
|--P. rugifrons van Lith 1974BM76
|--P. rugosus van Lith 1962BM76
|--P. saltitans Arnold 1958BM76
|--P. sandakensis (Rohwer 1923) [=Diodontus sandakensis]BM76
|--P. sapobaensis van Lith 1974BM76
|--P. schencki (Tournier 1889) [=Psen schencki; incl. Psen longulus Tournier 1889, Psen simplex Tournier 1889]BM76
|--P. scutatus (Rohwer 1921) [=Diodontus scutatus]BM76
| |--P. s. scutatusBM76
| |--P. s. borneensis (Rohwer 1923) [=Diodontus borneensis]BM76
| |--P. s. mindanaoensis (Rohwer 1923) [=Diodontus mindanaoensis]BM76
| `--P. s. sibuyanensis van Lith 1962BM76
|--P. scutellatus Turner 1912BM76
|--P. segrex van Lith 1972BM76
|--P. separatus van Lith 1962BM76
|--P. sinclairi Lal 1939BM76
|--P. singularis van Lith 1962bM76
|--P. sogatophagus Pagden 1933BM76
|--P. stevensoniR54
|--P. stuckenbergi Arnold 1962BM76
|--P. suifuensis van Lith 1901BM76
|--P. suluensis van Lith 1970BM76
|--P. taihorinus Strand 1915BM76
|--P. tanakai Tsuneki 1959BM76
|--P. thaianus Tsuneki 1974BM76
|--P. trevirus Leclercq 1961BM76
|--P. trimaculatus van Lith 1962BM76
|--P. trisulcus (Fox 1898) [=Psen trisulcus; incl. Diodontus corusanigrens Rohwer 1920, D. sulcatus Malloch 1933]BM76
|--P. tuberculifrons (Rohwer 1921) [=Diodontus tuberculifrons]BM76
| |--P. t. tuberculifronsBM76
| `--P. t. decoratus van Lith 1962BM76
|--P. turneri Arnold 1927BM76
|--P. uelleburgi van Lith 1974BM76
|--P. varius van Lith 1962BM76
|--P. xanthognathus Rohwer 1910BM76
| |--P. x. xanthognathusBM76
| `--P. x. centralis van Lith 1969BM76
|--P. xanthonotus van Lith 1969BM76
`--P. yoshimotoi van Lith 1969BM76
|--P. y. yoshimotoiBM76
`--P. y. pontilis van Lith 1970BM76

Psenulus Kohl 1896 [incl. Eopsenulus Gussakovskij 1934, Neofoxia Viereck 1901, Nipponopsen Yasumatsu 1938, Stenomellinus Schulz 1911]BM76

Psenulus frontalis (Fox 1898) [=Psen frontalis; incl. Diodontus hesperus Pate 1944, D. occidentalis Malloch 1933 non Fox 1892]BM76

*Psenulus fuscipennis (Dahlbom 1843) [=Psen fuscipennis; incl. Psen dufouri Dahlbom 1845, Psen nigratus Dahlbom in Brischke 1862, Psen nylanderi Dahlbom 1845, Psen procerus Costa 1871]BM76

Psenulus pallipes (Panzer 1798)BM76 [=Sphex pallipesBM76; incl. Trypoxylon atratum Fabricius 1804BM76, *Neofoxia atrataBM76, Psen atratusBM76, Trypoxylon (Pison) atratumG20, Psenulus brevitaris Merisuo 1937BM76, Psenulus gussakovskij van Lith 1973BM76, Psen haemorrhoidalis Costa 1871BM76, Psen minutus Tournier 1889BM76, Psen montanus Costa 1868BM76, Psen nigricornis Tournier 1889BM76, Psenulus puncticeps Gussakovskij 1933 non Psen puncticeps Cameron 1907BM76, Psenulus rubicola Hartig 1931BM76]

Psenulus puncticeps (Cameron 1907) [=Psen puncticeps; incl. Diodontus antennatus Rohwer 1923 non Xylocelia antennata Mickel 1916]BM76

*Type species of generic name indicated


[BM76] Bohart, R. M., & A. S. Menke. 1976. Sphecid Wasps of the World. University of California Press: Berkeley.

[G20] Goldfuss, G. A. 1820. Handbuch der Naturgeschichte vol. 3. Handbuch der Zoologie pt 1. Johann Leonhard Schrag: Nürnberg.

Krombein, K. V. 1979. Catalog of Hymenoptera in America North of Mexico vol. 2. Apocrita (Aculeata). Smithsonian Institution Press.

Malloch, J. R. 1933 Review of the wasps of the subfamily Pseninae of North America (Hymenoptera: Aculeata). Proceedings of The United States National Museum 82 (26): 1–60.

Melo, G. A. R. 1997. Silk glands in adult sphecid wasps (Hymenoptera, Sphecidae, Pemphredoninae). Journal of Hymenoptera Research 6: 1–9.

Pate, V. S. L. 1944. Synonymical notes on the psenine wasps (Hymenoptera, Sphecidae). Canadian Entomologist 76 (7): 133.

[R54] Rayment, T. 1954. Taxonomy, morphology and biology of sericophorine wasps with diagnoses of two new genera and descriptions of forty new species and six sub-species. Memoirs of the National Museum, Melbourne 19: 11–105.

[TB20] Taylor, C. K., C. Barthélémy, R. C. S. Chi & B. Guénard. 2020. Review of Psenulus species (Hymenoptera, Psenidae) in the Hong Kong SAR, with description of three new species. Journal of Hymenoptera Research 79: 169–211.

Leave a comment

Your email address will not be published. Required fields are marked *