Callipogon relictus Semenov belongs to the longhorn beetle family (Coleoptera: Cerambycidae) and is one of the largest beetle species in the Palearctic region, occurring in the Korean Peninsula, Russian Far East, and Mongolia (Lee et al., 2018;Yi et al., 2018). In South Korea, C. relictus has been designated as a Class I endangered species by the Ministry of Environment and as a Natural Monument No. 218 by the Korean Cultural Heritage Administration. Since 2006, the Korea National Arboretum (KNA) has been conducting intensive research on its biological features and habitat to aid its conservation in South Korea. During a survey of C. relictus habitat in Gwangneung Forest in 2020, we found three live larvae of C. relictus within cut logs of Quercus serrata Thunb. ex Murray (Fagales: Fagaceae). In this communication, we report Q. serrata as a new host plant of C. relictus and describe the morphometric characteristics of the three larvae, which will be useful for species conservation measures (Figs. 1-2; Table 1). Additionally, we provide an updated list of C. relictus host plants, with the addition of Q. serrata (Table 2).

Materials and Methods

In 2020, field surveys to identify host plants of C. relictus were carried out in Gwangneung Forest, which surrounds the KNA in Gyeonggi Province, South Korea. Trees were visually examined for signs and symptoms of C. relictus infestations, including holes made by C. relictus adults and feeding scars made by larvae. A tree dissection was performed in the field, with suspect trees being cut and split along the larval galleries.

On February 24, 2020, we found defoliated logs of Quercus (Fagaceae) near a trail path in the KNA (37° 45ʹ 5.5ʺ N, 127° 10ʹ 0.7ʺ E, altitude 80 m) (Fig. 1A). It was assumed that the trees had been felled to clear the trail of obstructions for tourists. One of these trees showed signs of larval infestations. It had been cut approximately 90 cm above the earth, and its diameter at breast height was approximately 80 cm. The total length of the cut logs was approximately 680 cm. The upper part of the trunk was cut off and could not be measured.

The morphometric characteristics of the live larvae, such as length, head width, and weight, were measured. The list of host plants provided by Lee et al. (2019) was used as a reference to confirm Quercus as a new host plant.

Results and Discussion

We observed a dead broadleaved tree bearing holes and feeding scars made by the larvae (Fig. 1B–E). Dissection of the tree along the larval galleries and feeding traces (Fig. 1B, C, D, E) revealed three large live C. relictus l arvae within the galleries ( F ig. 1B, E). We concluded that the galleries were made by C. relictus larvae. The tree in which the larvae were observed was identified as Quercus serrata Thunb. ex Murray (Fagales: Fagaceae), commonly called Jolcham oak. This species has not been previously recorded as a host plant of C. relictus.

The first larva was 74 mm in length, 10.19 mm in head width, and 9.42 g in weight (Fig. 2A, B). The second larva was 72 mm in length, 10.28 mm in head width, and 9.89 g in weight (Fig. 2C, D). The third larva was 82 mm in length, 9.54 mm in head width, and 11.93 g in weight (Fig. 2E, F). The first, second, and third larvae were found 370 cm, 345 cm, and 285 cm, respectively, from the ground, and all were approximately 20 cm inside the bark (Fig. 1E).

In the present communication, we report Quercus serrata Thunb. ex Murray as a new host of Callipogon relictus and provide an updated list of host plants of C. relictus (Table 2).