While checking out the Yellow Assassin Bug Cosmolestes picticeps in the park in relation to last week’s post, I came across a small rounded fern-feeding beetle. The body was black in colour with 2 large round reddish-orange patches on its hard wing case (elytra). Its size was less than 5 millimetres. The fern under attack was the Giant Sword Fern (Nephrolepis biserrata), a very common wild fern in the park.

The search for its identity began. The first candidate was Schenklingia bhaumiki that feed on a wide range of ferns and found in India. The adult beetles are small (2.25 mm in length, 1.90 mm in width), somewhat rounded, reddish brown with 5 pairs of black spots on the elytra as described by the publication [1]. The pattern on the elytra did not match the one I saw.

The second candidate was Ivalia haruka found in Malaysia but it feeds on mosses. It is about 2.5 mm in length with a black rounded body and each elytron has a reddish-orange round spot narrowly margined by yellow stripe [2]. This one seemed to be closed based on the picture of the dried specimen shown in the publication except that it feeds on mosses instead of fern.

Where the Giant Sword Fern was located, there was another look-alike fern, Asplenium longissimum. While the Giant Sword Fern was a resident flora in that area, Asplenium longissimum was planted by NParks when the park underwent upgrading a few years back. Besides having very long fronds (leaves), Asplenium longissimum bears plantlets on its fronds along the rachis. The features of their sori (spore-producing structures) are also very different. Though the 2 ferns were growing together, the beetles only attacked the Giant Sword Fern. After browsing through my beetles’ photo deck, old photos of this beetle were found. I had already seen this beetle in this same park in November 2018 but had not discover its relationship with the fern back then. It is probably a leaf beetle from the (family Chrysomelidae).

Though I failed to identify the beetle, all was not loss. While searching for this beetle online, I unlocked the genus of an unknown weevil in my photo deck. This unique-looking beetle was sighted back in March 2019. It turned out to be a Cionus species, a weevil from the family Curculionidae.

Besides the unknown fern-feeding beetle, I came across 3 other beetle during the walks in the park, namely a Handsome Fungus Beetle (Eumorphus quadriguttatus), an unknown Darkling Beetle and a Longhorn Beetle (Coptops annulipes).

References:

[1] Patra B, Bera S. Herbivore damage to ferns caused by a Chrysomelid beetle from Lower Gangetic Plains of West Bengal, India. Am Fern J 2007;97(1):19–29. | Read article |

[2] Takizawa H, Konstantinov AS. The genus Ivalia Jacoby 1887 (Coleoptera: Chrysomelidae: Galerucinae: Alticini) of the mount Kinabalu, Sabah, Malaysia. J Insect Biodiversity 2018;6(1):1-23. | Read article |