- First tarsal segment shorter than second and third also shorter than second
- Anterior margin of pronotum truncate, concave or deeply emarginate- Lateral teeth more prominent than median teeth.
The genus Heterobostrychus is defined by:
- Body length: 5.0-16.0mm
- Head capsule not deeply and transversely constricted behind eyes- Gena without a large tooth or lobe below each eye
- Antennal club segments with two unmargined and indistinct nearly circular sensory areas- Pronotum excavated behind the middle of the anterior margin.
There are 5 known species in Heterobostrychus: H. aequalis, H. brunneus, H. hamatipennis, H. pileatus and H. unicornis.
Females differ from males as: pronotum smaller, teeth on anterior apical border of pronotum shorter; apical declivity of elytra without marginal tubercles.
Heterobostrychus aequalis is characterised by:
- Apical declivity and elytra bare
- Pronotum with obvious posterior angles, often lobed- Frons without a distinct hairy gibbosity
- Pronotum middle of basal half sparsely punctured (females) or densely punctured (males)- Second segment of hind tarsus noticeable shorter than the last segment.
Graham Goodyer (2008). Identification of Bostrichid Beetles to Genus and Species (unpublished)
Differentiation of males as follows:
1. Apical declivity of elytra unituberculate on each side ..
H. hammatipennis- Apical declivity of elytra bituberculate on each side .. 2
2. Posterolateral angles of pronotum lobed; teeth on anterior border of pronotum broadly separated; apical declivity of elytra arcuately deflexed with inner two stout tubercles pointing obliquely upwards ..
- Posterolateral angles of pronotum rounded; teeth on anterior border of pronotum narrowly separated; apical declivity of elytra obliquely deflexed with inner two stout tubercles pointing inwards ...H. pileatus