Judul: Natural Enemies of Spodoptera frugiperda Larvae (Lepidoptera:  Noctuidae) on Corn in Sekoto Village, Badas District, Kediri Regency
Abstrak: Spodoptera frugiperda adalah hama penting pada tanaman jagung yang berasal dari daerah tropis Amerika. Larva ini bersifat polifag sehingga dapat menyebabkan kerusakan hasil pada berbagai jenis tanaman, terutama tanaman jagung yang mengalami kerusakan mencapai 20–80% pada populasi tinggi. Populasi tinggi S. frugiperda di beberapa negara disebabkan tidak adanya musuh alami. Meskipun demikian, keberadaan musuh alami lokal yang memangsa S. frugiperda dapat menekan populasi hama ini. Penelitian ini bertujuan mengetahui musuh alami dari Spodoptera frugiperda di Desa Sekoto, Kecamatan Badas, Kabupaten Kediri, Jawa Timur. Penelitian dilakukan dengan melakukan pengamatan di lahan dan pemeliharaan larva. Pemeliharaan larva dilakukan untuk mengamati musuh alami yang muncul dari tubuh larva yang berasal dari lahan. Identifikasi musuh alami dilakukan menggunakan sumber pustaka dan berdasarkan pengamatan morfologi dari musuh alami. Musuh alami yang ditemukan dilahan adalah cendawan entomopatogen, bakteri entomopatogen, dan parasitoid. Berdasarkan hasil pemeliharaan, persentase populasi musuh alami tertinggi secara berurutan adalah cendawan entomopatogen, parasitoid, dan bakteri entomopatogen.
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Judul: Spodoptera frugiperda (J. E. Smith) (Lepidoptera:  Noctuidae): Attacks and Their Natural Enemies on Corn in Munte Village, Munte Sub district, Karo District, North S
Abstrak: Spodoptera frugiperda (Lepidoptera: Noctuidae) is a relatively new pest in Indonesia and an essential pest of the corn. Corn cultivation is dominant in Munte village. This study aimed to estimate the damage caused by S. frugiperda, inventory natural enemies, estimate parasitization level of parasitoids and population of predator and observe entomopathogen fungi in Munte Village, Karo District, North Sumatera. Observations were conducted on an area of ± 2500 m2 . Damage level were observed on five plots, each consist of 20 plants with an interval of one plant. Larvae and eggs were collected and reared in the laboratory, as well as suspected predatory insects. The level of damage from each observation for 8 weeks after planting (WAP) reached > 30% or was classified as heavy. Natural enemies found were parasitoids, predators, and entomopathogenic fungi groups. The parasitoids belong to Hymenoptera and Diptera, the proportion of population were 29.71% Telenomus sp. (Hym.: Scelionidae), 3.40% Trichogramma sp. (Hym.: Trichogrammatidae), 1.65% Microplitis sp. (Hym.: Braconidae), 0.41% Charops sp. (Hym.: Ichneumonidae), 1.23% Anomaloninae (Hym.: Ichneumonidae), 0.41% Megaselia sp. (Dipt.: Phoridae), and 0.41% of Tachinidae (Diptera). The other natural enemies found were predators Doru sp. (Der.: Forficulidae) and Oxyopes sp. (Ara.: Oxyopidae), entomopathogenic fungi was Metarhizium sp. Telenomus sp. wasthe most found in the field and had potentially reduced the eggs of S. frugiperda.
Keyword: damage level, parasitoid, parasitization level, predator

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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