In Indonesian national economics, maize is a second food source after rice. The production of maize in some aspect is affected by the presence of insect particularly Orthopteran Order. The information of advantage and disadvantage of insects is useful for farmers. This research aimed to determine the species of Orthopteran and it is role to maize plant in the Village Kesiman, Denpasar. This research was conducted from December 2015 to February 2016. Insect was collected using sweeping net accordingly in each plot of maize plants. The plot was square form with the size of 10 m x 25 m. The sample was collected from the maize plant in the Ve phase until physiological maturation phase. in each phase, from 07.00 am until 10.00 am Bali time. Sample was collected for 15 minutes per plot and repeated three times. The insects collected was identified, and the insect density was predicted following Krebs (1989). As many as 242 individual insect which belong to Orthopteran Order was collected. Those belong to 8 families and 25 species. The species were Atractomorpha sp., Orchelimum sp., Phlaeoba sp., Gastrimargus sp., Urnisiella sp., Metaleptea brevicornis, Xenocatantops sp., Scudderia sp., Calolampra sp., Eritettix sp., Platyzoteria sp., Conocephalus strictus, Morabine sp., Acrida sp., Tenodera sp., Stagmomantis sp., Blattela sp., Periplaneta sp., Tettigidea lateralis, Mantis sp., Gryllus sp., and Anaxipha exigua, Tettigidea sp. 2, Tettigidea sp. 1, and unidentified (species x). Families that act as omnivores are Family Blattidae and Grillidae, families that act as herbivores are Pyrgomorphidae, Acrididae, Tettigonidae, Eumastacidae, and Tetrigidae, while families that act as predators are Mantidae.
 Keyword : maize, orthopteran, insect species, insect role.

It has been conducted a research that aims to determine the ratio of essential oil content of citronella stalks (Cymbopogon nardus Rendle L.) grown in the lowlands of Denpasar and the highlands of Bedugul. The experiment was conducted by using experimental designs. The parameters measured were the volume and the level of citronella oil produced. The sample preparation of powdered citronella stalks was as much as 200 grams, macerated with 96% ethanol and evaporated with Vacuum rotary evaporator to form condensed extract. The research used quantitative methods. The volume of hydro distillation was to obtain a crude extract of citronella stalks and the identification of active compounds was conducted by using Gas Chromatography / Mass Spectrometry (GC-MS). It can be concluded that the levels of citronella essential oil stalks from the highland of Bedugul was higher than the lowland areas of Denpasar, while the quality of essential oil of the lowland of Denpasar was better than that of the Bedugul highland. The content of secondary metabolites of the results of GC-MS analysis obtained from the essential oils contained in the analyzed crude extract of citronella stalks namely the compound of Selina-6-en-4-ol (2287322), the compound of n-hexadecanoic acid (1238019) and the compound of Driman-8,11-diol from the lowland of Denpasar while the Selina compound-6-en-4-ol (1856137) from the highland of Bedugul.
 Keywords: Citronella, essential oil content, altitude