1. Introduction

Acanthaspis is a genus (Reduviidae: Reduviinae) of assassin bugs found in Africa and parts of Asia. The most recent large publication concerning the oriental species deals with species found in China. You can read more about the genus there.

Currently there are three Acanthaspis species known from Singapore on the Biodiversity of Singapore website: Acanthaspis inermis Stål, 1870, Acanthaspis nr. quadriannulata, and Acanthaspis signifera Stål, 1863. This species is not an Acanthaspis species, but most likely a female Psophis species. Here are some comments I have on the former two:

2. Acanthaspis inermis

A. inermis was described by Stål from the Philippines. Images of the type can be found here. Another image can be found on the Heteroptera Species Pages, which was collected from Zamboanga, Mindanao. With that in mind, here are some other iNaturalist observations I think may be A. inermis:
https://www.inaturalist.org/observations/209125303
https://www.inaturalist.org/observations/209127898
https://www.inaturalist.org/observations/115355948
https://www.inaturalist.org/observations/115555711

Besides the BoS website, more pictures of the “A. inermis” from Singapore can be found in iNaturalist:
https://www.inaturalist.org/observations/195675300
https://www.inaturalist.org/observations/101995084
https://www.inaturalist.org/observations/216458610
I’ve noticed some consistent differences between the Singaporean and Filipino individuals, which I attempt to illustrate by comparing observation 115555711 by hrc_habitat21 and 216458610 by moniquecordeiro. These include:

1. Scapus dark brown basal half + pale yellow apical half (S1) vs pale yellow throughout with small dark brown annulation(s) (P1)
2. Anterior pronotal lobe more or less uniformly dark brown (S2) vs with clear pale yellow elevated regions (P2)
3. Outer membrane cell without pale spot (S3) vs with a pale spot basally (P3)

These differences can also be observed in all the other links I posted. Acanthaspis species can vary in colour intraspecifically, some documented examples include Acanthaspis siva Distant, 1904 (posterior pronotum and legs), Acanthaspis cincticrus Stål, 1859 (mostly posterior pronotal lobe), and Acanthaspis quinquespinosa (Fabricius, 1781) (posterior pronotal lobe). Despite that, I still think these differences are enough to suggest the species in Singapore isn’t A. inermis, especially character 3.

The species from Singapore is more comparable to Acanthaspis laoensis Distant, 1919, although there are still come differences like A. laoensis having a uniformly black scape and also generally more colour on the anterior pronotal lobe (example).

3. Acanthaspis quadriannulata

This species from Singapore with four large round spots on the posterior pronotum, spinose humeral angles, and an elongate head is often labelled as A. quadriannulata:
https://www.inaturalist.org/observations/195669936
https://www.inaturalist.org/observations/203333735
https://www.inaturalist.org/observations/214311169

The characters I mentioned make it visually similar to Acanthaspis collaris Hsiao, 1976, which received an updated description in the Chinese Acanthaspis revision. On page 20 you can find remarks comparing it to A. quadriannulata and Acanthaspis flavovaria (Hahn, 1834). In particular I would like to highlight this statement:

A. collaris is also similar to A. flavovaria in body plan, however, it can be distinguished from the latter in each femur with two annulations and tibiae are bicolourous (vs. each femur with one annulation on subapical portion and tibiae are unicolourous in A. flavovaria).

The leg colouration (femora and tibia with two annulations) on A. collaris is similar to that of A. quadriannulata. The Singapore species, on the other hand, only has one subapical yellow annulation on the femora and unicolorous tibiae, making it much closer to A. flavovaria. Acanthaspis flavovaria was first described from Java, so the species identity may apply to these individuals, which look very much like the species from Singapore:
https://www.inaturalist.org/observations/131289359
https://www.inaturalist.org/observations/142052493

Posted on May 19, 2024 10:55 AM by eggshe11