Guide to Tenebrionids of Bahia de los Angeles

The islands in the Gulf of California provide a natural laboratory for the effects of “spatial subsidy,” the movement of resources from a rich environment (the sea) to a more impoverished habitat (the desert islands). In this context, scientists have studied many species on the islands, including Tenebrionid beetles.

Satellite map of ahia de Lo — Map of the bay at Bahia de los Angeles. Most islands, including all islands sampled this year, are labeled. The town of Bahia de los Angeles is labeled at lower left.

Below is a draft guide to the beetles found on the islands, When possible, photos are provided of beetles held in fingers and mounted on the photography platform. Cartoons provide graphic representation of the relative sizes of the beetles, ranging from tiny (Batuliodes) to hefty (Cryptoglossa), keeping in mind that the sizes of all species can vary significantly.

Distributions of each species are based on data from Sanchez Piñero and Aalbu (2002). A table extracted from their observations can be found here.

Click the photographs if you want to see larger versions.

Argoporis apicalis

Medium sized, with ridged elytra and reddish legs. Argoporis is one of the few Tenebrionids on the islands which possess defensive glands in their abdomens.

Found on all islands except Mitlan (tiny island next to Coronado).

narrow black beetle with reddish legs held by fingers — *Argoporis apicalis* trapped on Coronadito island. 6/26/25.

*Argoporis apicalis* trapped on Cerraja island. The blurred image of an extra antenna was caused by using focus stacking to improve depth of field. 6/27/25.

Batuliodes confluens

This tiny brown beetle with roughened pronotum and elytra.

Found on the majority of islands, and may be undercounted due to its small size.

tiny black beetle on a white background — ~3 mm

*Batuliodes confluens* trapped on Flecha island. 6/23/14

*Batuliodes confluens* trapped on Cerraja island. 6/27/25.

Cryptadius tarsalis

Small, oval, and deep-bodied, with dense rows of small punctures on the elytra.

Cryptadius is found on Bota, Cerraja, Coronado, Jorobado, Mitlan and Pata.

Diagram of a small beetle on a white background — 8 mm

*Cryptadius tarsalis*.trapped on Llave island. Scale bar, 2 mm. 6/27/25

Cryptoglossa spiculifera

One of the largest beetles on the islands, with elytra decorated with rows of raised, spiny bumps.

Found on the largest islands (Coronado, Cabeza de Caballo, but not La Ventana) as well as the rookery island, Gemelos West.

diagram of a black beetle almost filling a white background. — 28 mm

*Cryptoglossa spiculifera* trapped on Gemelos West island, 6/28/25.

Large black beetle on blurred blue background. — *Cryptoglossa spiculifera* trapped on Gemelos West island. Scale bar, 10 mm. 6/28/25.

Microschatia championi

Slightly smaller than Cryptoglossa, the elytra of Micoschatia are decorated with dimples rather than sharp bumps and there are punctures on the lateral pronotum of M. championi.

Present on all but the smallest islands.

*Microschatia championi* trapped on Cerraja island. 6/27/25.

*Microschatia championi* trapped on Cerraja island. Scale bar, 5 mm. 6/27/25.

Stibia sparsa

Shaped like a typical Tenebrionid, with dense punctures on the pronotum and rows of punctures on the elytra.

Stibia can be found on the largest islands (Cabeza de Caballo, Coronado, La Ventana) plus Gemelos West.

diagram of a black beetle on a large white background — 11 mm

small brownish black beetle held in fingers — *Stibia sparsa* trapped on Gemelos West island. 6/28/25

dorsal view of black beetle on blurred blue background — *Stibia sparsa* trapped on Gemelos West island. Scale bar, 2 mm. 6/28/25.

Tonibius sulcatus

Very small and reddish, with relatively smooth pronotum and strongly ridged elytra.

Described from most islands, except Coronaditio, Gemelos West, Jorobado and Llave.

diagram of a very small black beetle on a white background — 6 mm

*Tonibius sulcatus* found at Las Hamacas hotel. 7/10/24.

Triphalopsis californicus

Small, black, oval, and deep-bodied. Covered with fine hairs that are often coated in dust.

Triphalopsis has been described from all islands except Gemelo West.

*Triphalopsis californicus* trapped on Flecha island. 6/27/25.

*Triphalopsis californicus* trapped on Cerraja island. Scale bar, 2 mm. 6/27/25.

There are many other beetles, including various species of Histeridae and Dermestidae (not shown).

Hister Beetle on Coronadito Island. Scale 2 mm. 6/26/25.

References

Sanchez Piñero, F. and Aalbu, R. L. (2002). Tenebrionid Beetles (Appendix 6.1). In A New Island Biogeography of the Sea of Cortés, pp. 129–153. New York: Oxford University Press.