PHYSIOLOGICAL ECOLOGY Effects of the Activity of Coprophagous Insects on Greenhouse Gas Emissions from Cattle Dung Pats and Changes in Amounts of Nitrogen, Carbon, and Energy MITSUHIRO IWASA, 1,2 YUKARI MOKI, 1 AND JUNICHI TAKAHASHI 3 Environ. Entomol. 44(1): 106–113 (2015); DOI: 10.1093/ee/nvu023 ABSTRACT Effects of coprophagous insects on greenhouse gas emissions from cattle dung pats were investigated during the initial stage in the decomposition of dung, with accompanying changes in nitro- gen, carbon, and energy content. We set up three treatments with adults of Caccobius jessoensis Harold (dung beetle) and larvae of the fly Neomyia cornicina (F.): 1) dung with dung beetles; 2) dung with fly lar- vae; and 3) dung without insects. In these treatments, the gas flux was measured from air flow exiting the glass containers connected with an in vitro continuous gas analysis system. Total gas fluxes from dung pats with fly larvae were lowest in carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O). The presence of dung beetles significantly increased CO 2 flux from dung, but reduced CH 4 flux compared with dung without insects. Fluxes of N 2 O from dung pats with dung beetles and without insects had dis- tinct peaks at different times after the start of the experiment, while N 2 O from dung with fly larvae was emitted in extremely low levels throughout the experiment. Carbon (C) content in dung with beetles was significantly lower than that of untreated dung pats designated as fresh dung, whereas that of dung with fly larvae was higher than dung with beetles and without insects. Nitrogen (N) content was significantly lower in dung with fly larvae than the other treatments. Contents of C and N in fly pupae were 35.87 and 8.05%, respectively. During the larval growth of the fly, energy accumulated in the fly body was 2,830 J/g. KEY WORDS CH 4 , CO 2 , dung beetle, fly larva, N 2 O Introduction Many dung-feeding insects inhabit cattle dung pats in pastures. Of these various coprophagous insects, dung beetles and fly larvae have been shown to play an im- portant role because they are involved in dung decom- position through their feeding behavior and movement within dung (Papp 1970, Nakamura 1975, Holter 1979). Through burying behavior in soil, dung beetles decompose coarse dung fibers and return nitrogen (N) and water from dung to the soil (Yokoyama and Miyau- chi 1990, 1991; Yokoyama et al. 1991b; Brown et al. 2010). They influence the soil under dung and acceler- ate growth of the plants in pastures (Bornemissza and Williams 1970, Bang et al. 2005, Nichols et al. 2008). Meanwhile, fly larvae actively move within dung and feed on it, thus incorporating its nitrogen (N) compo- nents into the body and decreasing the N content in the dung (Macqueen and Beirne 1975). Helsel and Wicklow (1979) reported on the role of sciarid fly lar- vae in energy transformations in the process of decom- position of rabbit feces. However, those studies on the activities of these insects are mainly focused on the feces decomposing process, degradation potential of dung beetles, physical and chemical effects on dung, and influence on plant growth. Cattle dung pats emit various gases and are an an- thropogenic source of greenhouse gases (Macdiarmid and Watkin 1972, Holter 1991, Petersen et al. 1998, Saggar et al. 2004, Van Groenigen et al. 2005, Bellarby et al. 2013). Studies of greenhouse gases from cattle dung have focused on field surveys of greenhouse gas emission during dung composting in livestock barns and its inhibition (Masse ´ et al. 2002; Kreuzer et al. 2002; Shiraishi et al. 2004, 2006; Kreuzer and Hin- drichsen 2006; Mwenya et al. 2006). Reports on cattle dung pats in pastures have shown only greenhouse gas emission from dung pats and the concentration (Holter 1990, 1991, 1997; Jarvis et al. 1995) and loss of N and ammonia (NH 3 ) as volatile gases as a result of dung beetle activities (Gillard 1967, Yokoyama et al. 1991a). Penttila ¨ et al. (2013) recently reported that dung bee- tles increase the generation of carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) from cattle dung pats, but de- crease methane (CH 4 ) generation. However, the rela- tionship between the activity of insects living in dung and greenhouse gas generation has not sufficiently been described, and the influence of fly larvae on greenhouse gas emission is still unknown. Therefore, we aim to determine the effects of the activities of dung beetles and fly larvae on greenhouse gases 1 Laboratory of Entomology, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido, 080-8555 Japan. 2 Corresponding author, e-mail: iwasa@obihiro.ac.jp. 3 Department of Animal and Food Hygiene, Obihiro University of Agri- culture and Veterinary Medicine, Obihiro, Hokkaido, 080-8555 Japan. V C The Author 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com Downloaded from https://academic.oup.com/ee/article/44/1/106/2464838 by guest on 02 July 2022