Biogeography 18. 59–62. Sep. 20, 2016 Life history of two endangered wetland Pterostichus (Coleoptera: Carabidae) ground beetle species as revealed by laboratory rearing experiments Kôji Sasakawa* Laboratory of Zoology, Department of Science Education, Faculty of Education, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba-shi, Chiba, 263-8522 Japan Abstract. Elucidating the basic life history of endangered species is the first important step in their conser- vation. In this study, two endangered wetland ground beetles, Pterostichus (Eurythoracana) kajimurai Habu & Tanaka, 1957 and Pterostichus (Badistrinus) bandotaro Tanaka, 1958 (Coleoptera: Carabidae), were reared under laboratory conditions and their life histories were examined. This revealed that the life histories of the two species were almost identical. Females that were collected in late April and fed mealworms oviposited into mud and larvae emerged from the mud after hatching. Larvae refused earthworms or snails as food, but developed to adulthood on the mealworm diet. The fertility of the emerged adults (males and females in P. ka- jimurai, females in P. bandotaro) was confirmed by laboratory rearing in the following spring. The time from hatching to adult eclosion at 24°C was at least 45 days for P. kajimurai and at least 41 days for P. bandotaro. Key words: larval feeding habits, oviposition behavior, Pterostichus bandotaro, Pterostichus kajimurai. In Japan, environmental degradation is proceeding using one female of each species collected from the rapidly, and many species are endangered. Insects Watarase wetland in Tochigi City, Tochigi Prefec- that inhabit wetlands or grasslands are severely ture, Japan, on 26–28 April 2013. Unless otherwise threatened, and conservation measures are urgent- stated, the experiment was conducted in an incubator ly needed (Ministry of the Environment of Japan, maintained at 22°C under a light:dark 16:8 h photo- 2012). Elucidating their basic life histories is the first period. Each female was reared in a Petri dish (6.0- important step in the conservation of such species. cm diameter, 1.5 cm high) filled to a depth of 0.5 This short communication reports the life histories cm with flooded garden soil (i.e., mud). Moistened of two endangered insect species, the ground bee- moss, which maintains high humidity and serves as tles Pterostichus (Eurythoracana) kajimurai Habu a shelter for beetles, was place on the soil surface. & Tanaka, 1957 and Pterostichus (Badistrinus) This rearing condition simulates a wetland environ- bandotaro Tanaka, 1958 (Coleoptera: Carabidae), ment, which is the habitat of both species. Commer- as revealed by a laboratory rearing experiment. The cial mealworms (Tenebrio molitor larvae, cut into two species inhabit wetlands, and both are listed pieces) were provided as a food source ad libitum. in the local Red Lists of two and three prefectures, The food was replaced daily; at the same time, the respectively (Association of Wildlife Research and surfaces of the soil and moss were checked for the EnVision, 2007). presence of eggs/hatchlings. Laboratory rearing experiments were performed For P. kajimurai, 41 first-instar larvae were ob- ——————————————————————— tained on 9–27 May. For P. bandotaro, 27 first-instar *Corresponding author: [email protected] larvae were obtained on 11–14 May. These hatch- − 59 − Life history of two endangered wetland Pterostichus carabids lings were found on the soil surface. No individuals larvae usually hatch and molt in the soil, hatching were found at the egg stage in either species. Some and molting dates could not be determined in most of the obtained larvae were reared individually in a cases). Petri dish (3.5-cm diameter, 1.0 cm high) filled to a The fertility of the emerged adults was examined depth of 0.5 cm with moistened garden soil. Because the following spring. The rearing procedures were there was no information on the larval feeding habits identical to those of the parental females until the au- of the two species, three major types of animal diet tumn, after which the beetles were kept subject to a for carabid larvae (insect larvae, earthworms, and temperature change from autumn to spring. The bee- snails/slugs) were initially provided simultaneously tles were transferred individually to plastic bottles to early hatchlings. Following Sasakawa (2016a), (3.5-cm diameter, 3.5 cm height) filled to a depth of mealworms, Pheretima earthworms, and Brady- 2.0 cm with moistened moss and maintained under a baena snails (all cut into pieces) were used as the light:dark 0:24 h photoperiod at 15°C from 25 Sep- respective diet types. Larvae of both species ate only tember to 21 November, 10°C from 21 November to the mealworms, so only mealworms were provided 26 December, and 5°C from 26 December 2013 to subsequently. 16 April 2014. During the periods at 15°C and 10°C, In both species, all of the larvae fed mealworms mealworms were provided every 2–3 days. On 16 reached subsequent developmental stages, and no April 2014, the beetles were awakened, and the rear- individuals died due to unsuitability of the diet. Two ing experiment began. The rearing procedures were (one male and one female) and one (female) larvae identical to those of the parental females, except that reached adulthood in P. kajimurai and P. bando- the beetles were maintained under a light:dark 16:8 taro, respectively. Other individuals were killed at h photoperiod and a temperature cycle of 20°C (light) various developmental stages as specimens for tax- and 15°C (dark) and that the females were allowed onomic studies (Table 1). The time from first-instar to mate. For the P. bandotaro female, a conspecific entry to adult eclosion was 45 and 46 days for the P. male collected from the Watarase wetland on 26 kajimurai male and female, respectively. The corre- April 2014 was added to the Petri dish on 27 April. sponding value for the P. bandotaro female was 41 For the P. kajimurai female, because no wild male days. These results were compatible with the scarce was collected, the reared sibling male was added reliable data on the duration of each developmental to the Petri dish on 27 April (i.e., sib mating). The stage for the two species (Table 2; note that because beetles were reared until 8 May, and five and one Table 1. Data on rearing Pterostichus kajimurai and P. bandotaro larvae. Note that no individuals died due to unsuitability of the diet. L1 L2 L3 Pupa Adult Pterostichus kajimurai Number of individuals At the initial phase of each developmental stage 41 23 17 4 2 Mortality in each developmental stage 0 0 0 0 0 Killed as specimens 18 6 13 2 - Pterostichus bandotaro Number of individuals At the initial phase of each developmental stage 26 7 7 3 1 Mortality in each developmental stage 0 0 0 0 0 Killed as specimens 19 0 4 2 - − 60 − Kôji Sasakawa Table 2. Developmental duration [days; mean ± SD (n)] of Pterostichus kajimurai and P. bandotaro. Note that larvae usually hatched and molted in the soil, so the hatching and molting dates and resulting duration of each developmental stage could not be determined in most cases. L1* L2 L3 Pupa Pterostichus kajimurai 11 (1) 9.7 ± 1.2 (3) 18 (1) 9.5 ± 0.7 (2) Pterostichus bandotaro 9 (1) 11 ± 0 (2) - 9 (1) *When white hatchlings, which are observed only immediately after hatching, were found, the date was de- termined to be the hatching date. first-instar larvae were obtained from P. bandotaro are insect larvae feeders suggests that a requirement and P. kajimurai, respectively. for particular prey species is not the principal reason These results are notable in some aspects. First, it that the two species are endangered. became apparent that both species oviposit into mud. In wetland carabids, oviposition behavior has been Acknowledgements reported for some species, and it takes two forms. One is employed by Carabus clathratus Linnaeus, This study was partly supported by grants-in-aid 1761, Bembidion velox (Linnaeus, 1761), Nebria from the Japan Society for the Promotion of Science yatsugatakensis Sasakawa, 2016, and Elaphrus su- (no. 25830150). gai Nakane, 1987, which lay eggs in mud (Huk & Kühne, 1999; Kleinwächter & Bürkel, 2008; Sasaka- References wa, 2016b, unpublished data). The other is employed by some Chlaeniini species and Pterostichus (Nialoe) Association of Wildlife Research and Envision, isumiensis Kasahara & Saito, 1997, which glue mud 2007. Search System of Japanese Red Data (data- cells, each containing one egg, to substances on the base on the internet). [Cited 8 May, 2016] Avail- ground (Tanaka, 1956; Sasakawa, 2011). In B. velox, able from http://www.jpnrdb.com/index.html. (in which oviposits into mud as P. kajimurai and P. Japanese.) bandotaro do, ovipositing into mud enhances egg Holland, J. M., 2002. Agroecology of Carabid Bee- survival (Kleinwächter & Bürkel, 2008). If this is tles. Intercept Ltd., Andover, United Kingdom. also true of the two studied species, the maintenance Huk, T. & Kühne, B., 1999. Substrate selection by of a suitable ovipositing environment is vital for Carabus clatratus (Coleoptera, Carabidae) and its conservation. This issue needs to be addressed in the consequences for offspring development. Oecolo- future. The present study also revealed that the lar- gia, 121: 348–354. vae of the two species are insect larvae feeders that Kleinwäechter, M. & Büerkel, M., 2008. Offspring can attain full development on an insect larvae diet. performance in dynamic habitats: key factors In carabid larvae, earthworm feeders and snail/slug for a riparian carabid beetle. Ecol. Entomol., 33: feeders are specialist carnivores, and earthworms 286–292. and snails/slugs are essential for their development, Ministry of the Environment of Japan, 2012. Press whereas insect larvae feeders are usually generalist release: The fourth version of the Japanese Red carnivores that do not require particular prey species Lists.