Lyctus brunneus, illustrated by Des Helmore.

Belongs within: Bostrichoidea.
Contains: Bostrichinae.

The Bostrichidae are a group of beetles whose larvae are mostly borers in dead or dry wood. Many have a hooded, denticulate pronotum and/or straight antennae with free club segments. Gular sutures are confluent in members of the subfamilies Polycaoninae, Dinoderinae and Bostrichinae (Ivie 2002).

Powder-post beetles: got wood?
Published 29 November 2017
Jesuit beetle Bostrychopsis jesuita, from PaDIL.

Back when I was collecting insects in the Australian arid zone, one of the more easily recognisable animals that we would regularly come across was the jesuit beetle Bostrychopsis jesuita. I have no idea what gives them the name ‘jesuit beetle’, but these relatively large black beetles with their spiny pronotum with its two ‘horns’ coming off the front is not likely to be confused with much else. (Actually, now I think about it, could it be the horns that make them Jesuits? In which case, ouch.)

Bostrychopsis jesuita is one of the larger beetles belonging to the Bostrichidae, a family commonly going by the vernacular names of auger beetles or powder-post beetles. Both these vernacular names refer to the fact that many species in the family, particularly as larvae, are wood-borers (not fortune-tellers—that would make them augur beetles), with the ability to turn sapwood into a powdery frass. As a result, a number of species are notable timber pests. Other species, particularly the larger grain borer Prostephanus truncatus and the lesser grain borer Rhyzopertha dominica, are seed-feeders and pests in stored grain. A single genus, Endecatomus, is mycophagous, feeding on polypore fungi growing on dead hardwood trees (Liu & Schönitzer 2011). Bostrichids belong to a larger group of beetles, the Bostrichoidea, that are superbly adapted to feeding on dry foodstuffs (other members of the Bostrichoidea include the spider beetles of the Ptinidae and the carpet beetles of the Dermestidae). Modifications of the gut in most bostrichoids allow them to efficiently resorb water from the gut contents, and they can obtain pretty much all the moisture they need direct from the air.

Lesser grain borers Rhyzopertha dominica, from the US Department of Agriculture.

The bostrichids are divided between a number of subfamilies, members of which appear quite distinct from one another. Members of the Bostrichinae (to which Bostrychopsis belongs) and Dinoderinae are cylindrical and robust, with short sturdy legs. In some species, the rear of the body appears sharply cut off by a flat declivity in the rear of the elytra; this declivity can be by males to block the entrance to holes in the wood while the female is laying eggs deeper within (Lawrence & Britton 1991). Superficially, Bostrichinae can bear a close resemblance to another, unrelated group of wood-boring beetles, the bark beetles of the Scolytinae (I have to confess to confusing them myself when sorting specimens). The two groups can most readily be distinguished by their antennae, which are geniculate (elbowed) with a compact club in scolytines but non-geniculate with a loose clube in bostrichines.

A lyctine Trogoxylon impressum, copyright Udo Schmidt.

Members of other bostrichid subfamilies are not adapted to boring in wood as adults as well as as larvae, and as such are more elongate and less compact. The Lyctinae are more or less flattened, rectangular beetles that have been treated as a separate family in the past due to their distinct appearance. One group of lyctines, the Cephalotomini, are even more flattened than others, and are specialised for living as inquilines in the tunnels made by other bostrichids, feeding on their frass; their flattened bodies allow them to press themselves against the side of the tunnel and allow their host beetles to walk over them. Rather than boring deep into wood like bostrichines to lay eggs, females of species with non-boring adults use a long, flexible ovipositor to reach into cracks and other breaches in the tree’s bark (Liu & Schönitzer 2011).

Systematics of Bostrichidae

Characters (from Ivie 2002): Shape elongate, cylindrical or depressed, length 1.5–50 mm; color black, various shades of yellow and red-browns, rarely red or yellow with metallic green/blue markings; vestiture absent or variably  sparse to dense or patchy fine to scale-like setae. Head somewhat hypognathous, inserted into prothorax and usually not visible from above, some clearly prognathous and obvious from above; surface smooth, punctate or rugose. Antennae with eight to eleven antennomeres, straight, not geniculate, with club of two, three or four segments; rarely antennomeres of club strongly transverse, nearly lamellate, inserted laterally near eyes, above base of mandibles or in front of eyes under pronounced frontal angles. Labrum small, transverse; mandibles heavy, curved, apices often blunt, sometimes bifid; maxillary palpi with four palpomeres, small, slender; gula small, gular sutures distinct, mentum trapezoidal, labial palpi with three palpomeres, small, slender. Eyes prominent, bulging, small, oval. Pronotum large cowled or flat; shape subquadrate or anteriorly rounded; borders usually not margined; cowled species with anterior dorsal surface rough, rasp-like, some with curved horns or hooks; pleural region broad; some flattened types (Lyctinae) with a median depression, or median fovea; prosternum long to moderate in front of coxae; intercoxal process wide to absent; procoxal cavities open or closed behind. Mesosternum moderate. Metasternum broad, long. Legs with trochantins hidden; anterior coxae small, cylindrical to rounded, middle coxae round, nearly contiguous; hind coxae transverse, nearly contiguous to widely separate; trochanter obliquely or squarely attached to femur; femora broad to slender; tibiae slender, smooth, with single apical spur, tarsal formula 5-5-5, rarely 4-4-4, first tarsomere frequently very small, tarsomeres slender, simple. Scutellum small, triangular, oval, or quadrate. Elytra highly variable, usually coarsely punctate, with vague costae present, more rarely impunctate and plane; often with distinct apical declivity variously modified with spines; epipleural fold obscure. Hind wing well developed, in fully-veined species with characteristic bostrichoid venation, a short r3 attached to RP directly from rp-mp2 cross-vein, a well-developed R cell; folding with normal transverse folds. Abdomen usually with five ventrites, rarely six when morphological segment II is visible at base on each side; all segments  free,  sutures  entire. Malphigian tubules exhibiting bostrichiform modified cryptonephridy, hind gut with sclerotized ovoid rod that holds ““rectal pad””. Male genitalia bostrichoid, large and flattened horizontally with two basal struts distally curved, apically acute; parameres fused at the base or free; or trilobed. Median lobe long and stout, parameres long, stout, apically acute, convergent, freely articulated. Female genitalia with the paraprocts reduced to baculi; valvifers reduced; coxite membranous, setiferous; styli subapical. Larvae C-shaped; length 3 to 20 mm, rarely to 60 mm; vestiture absent, with a few short setae on the ventral surface or dense and fine; colour cream to dull white. Head retracted into prothorax or not, prognathous, elongate and flattened or subglobular. Antennae two- or three-segmented, simple. Clypeus and labrum distinct; mandibles symmetrical,  gouge-shaped, with or without  mola; maxillae with cardo, stipes and two- or three-segmented palpi; labial palpi one- or two-segmented. Stemmata single or absent. Thorax enlarged; meso- and metathorax sometimes with two plicae; legs five-segmented, with slender tarsungulus. Abdomen ten-segmented, with three or less distinct plicae dorsally on each segment; apical segments simple, ninth enlarged, tenth small, with anal pads. Spiracles annular or annular-uniforous; present on prothorax and abdominal segments one to eight.

<==Bostrichidae [Apatidae, Bostrychidae, Psoidae]
| i. s.: Acantholyctus corinifronsB14
| EnneadesmusB14
| |--E. forficulaB14
| `--E. trispinosusB14
| Psoa Herbst 1797 [incl. Acrepis LeConte 1852; Psoinae]I02
| |--P. dubia (Rossi 1792)B14
| |--P. italicaR26
| |--P. quadrisignataI02
| `--P. viennensis [=Bostrichus (Psoa) viennensis]G20
|--Dysides Perty 1832 [Dysidinae]I02
| `--D. obscurus Perty 1832I02
`--+--+--+--Euderia [Euderiinae]MW15
| | | `--E. squamosa Broun 1880B14
| | `--+--BostrichinaeMW15
| | `--PolycaoninaeI02
| | |--Melalgus Dejean 1835 [incl. Exopioides Guérin-Méneville 1884, Heterarthron Dejean 1836]I02
| | `--Polycaon Laporte 1836 [incl. Alloeocnemis LeConte 1853, Exops Curtis 1839]I02
| | |--P. femoralis Fab. 1792 [incl. P. plicatus]FS90
| | `--P. stoutii (LeConte 1853)I02
| `--DinoderinaeMW15
| |--Stephanopachys Waterhouse 1888I02
| |--Dinoderus Stephens 1830 [incl. Dinoderastes Lesne 1914]I02
| | `--D. minutus Fab. 1775 (see below for synonymy)FS90
| |--Prostephanus Lesne 1898I02
| | |--P. punctatusI02
| | `--P. truncatus (Horn 1878)B14
| `--Rhyzopertha Stephens 1830 [=Rhizopertha Guérin-Méneville 1845]I02
| |--R. collaris Erichs. 1842Mas86
| |--R. dominica (Fabricius 1792)I02
| |--R. elongatula Macleay 1872Mas86
| |--R. gibbicollis Macleay 1862Mas86
| |--R. obsipa Germ. 1848Mas86
| |--R. papuensis Macleay 1886Mac86
| `--R. religiosaMac86
`--Lyctinae [Lyctidae]MW15
| i. s.: LyctodonLB91
| TristariaLB91
| |--T. fulvipes Reitt. 1878M96
| |--T. grouvellei Reitt. 1878M96
| `--T. labralis Blackb. 1892M96
|--Trogoxylon LeConte 1861 [Trogoxylini]I02
| `--T. parallelopipedumI02
|--Lyctoxylon Reitter 1878I02
| `--L. japonum Reitter 1878I02
|--Minthea Pascoe 1866I02
| |--M. acanthacollisLB91
| |--M. rugicollis (Walker 1858)B14
| `--M. similata Pasc. 1863M96
`--Lyctus Fabricius 1792I02
|--L. brunneus Douglas 1876Mas86
|--L. canaliculatusR26
|--L. crenatusL02
|--L. frumentarius [=Colydium frumentarium]L02
|--L. hipposiderosB14
|--L. linearisRD77
|--L. microcephalus [=Paussus microcephalus]L02
|--L. minutus [=Ips minuta]L02
|--L. oblongusG20 [=Ips oblongaL02, Trogosita (Lyctus) oblongaG20]
|--L. planicollisI02
`--L. transversus [=Ips transversa]L02

Dinoderus minutus Fab. 1775 [incl. D. bifoveatus Woll. 1858, D. castanopterus Fairm. 1850, D. foveatus, D. pumilus, D. siculus Baudi 1873, D. substriatus, D. umbilicatus]FS90

*Type species of generic name indicated


[B14] Bouchard, P. (ed.) 2014. The Book of Beetles: A lifesize guide to six hundred of nature’s gems. Ivy Press: Lewes (United Kingdom).

[FS90] Fleutiaux, E., & A. Sallé. 1890. Liste des coléoptères de la Guadeloupe et descriptions d’espèces nouvelles. Annales de la Société Entomologique de France, 6e série 9: 351–484.

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

[I02] Ivie, M. A. 2002. Bostrichidae Latreille 1802. In: Arnett, R. H., Jr, M. C. Thomas, P. E. Skelley & J. H. Frank (eds) American Beetles vol. 2. Polyphaga: Scarabaeoidea through Curculionoidea pp. 233–244. CRC Press.

[L02] Latreille, P. A. 1802. Histoire Naturelle, générale et particulière des crustacés et des insectes vol. 3. Familles naturelles des genres. F. Dufart: Paris.

[LB91] Lawrence, J. F., & E. B. Britton. 1991. Coleoptera (beetles). In: CSIRO. The Insects of Australia: A textbook for students and research workers 2nd ed. vol. 2 pp. 543–683. Melbourne University Press: Carlton (Victoria).

[Mac86] Macleay, W. 1886. The insects of the Fly River, New Guinea, “Coleoptera”. Proceedings of the Linnean Society of New South Wales, series 2, 1 (1): 136–157.

[Mas86] Masters, G. 1886. Catalogue of the described Coleoptera of Australia. Part IV. Proceedings of the Linnean Society of New South Wales, series 2, 1 (2): 259–380.

[M96] Masters, G. 1896. Catalogue of the described Coleoptera of Australia. Supplement, part II. Dytiscidae, Gyrinidae, Hydrophyllidae, Staphylinidae, Pselaphidae, Paussidae, Silphidae, Scaphididae, Histeridae, Phalacridae, Nitidulidae, Trogositidae, Colydiidae, Cucujidae, Cryptophagidae, Lathridiidae, Mycetophagidae, Dermestidae, Byrrhidae, Parnidae, Heteroceridae. Proceedings of the Linnean Society of New South Wales 21 (Suppl.): 695–754.

[MW15] McKenna, D. D., A. L. Wild, K. Kanda, C. L. Bellamy, R. G. Beutel, M. S. Caterino, C. W. Farnum, D. C. Hawks, M. A. Ivie, M. L. Jameson, R. A. B. Leschen, A. E. Marvaldi, J. V. McHugh, A. F. Newton, J. A. Robertson, M. K. Thayer, M. F. Whiting, J. F. Lawrence, A. Ślipiński, D. R. Maddison & B. D. Farrell. 2015. The beetle tree of life reveals that Coleoptera survived end-Permian mass extinction to diversify during the Cretaceous terrestrial revolution. Systematic Entomology 40 (4): 835–880.

[RD77] Richards, O. W., & R. G. Davies. 1977. Imms’ General Textbook of Entomology 10th ed. vol. 2. Classification and Biology. Chapman and Hall: London.

[R26] Risso, A. 1826. Histoire naturelle des principales productions de l’Europe méridionale et particulièrement de celles des environs de Nice et des Alpes maritimes vol. 5. F.-G. Levrault: Paris.

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