Judul: Biodiversitas Predator Ngengat Sutra Samia, Samia cynthia ricini (Lepidoptera: Saturniidae)
Abstrak: Ngengat sutra Samia cynthia (Lepidoptera: Saturniidae) merupakan salah satu spesies serangga yang memproduksi serat sutra. Ngengat sutra samia sudah mengalami domestikasi, sehingga mudah dibudidayakan dengan pakan daun singkong karet dan jarak kepyar. Predasi ngengat sutra S. cynthia umumnya terjadi pada fase pradewasa. Predator berperan penting sebagai agen pengendali alami dalam ekosistem. Tujuan dari penelitian ini adalah mengukur keanekaragaman dan mendeskripsikan predator pada S. cynthia. Telur, larva, dan pupa S. cynthia dimasukkan dalam kotak pemeliharaan dan diletakkan di ruang terbuka sehingga predator dapat mengaksesnya. Hasil penelitian ditemukan sebanyak 15 spesies predator S. cynthia yang termasuk dalam 3 kelas, yaitu Arachnida, Insecta, dan Reptilia. Predator yang ditemukan dominan yaitu Dolichoderus thoracicus, Tapinoma melanocephalum, dan Iridomyrmex anceps. Keanekaragaman predator sutra Samia tergolong rendah dengan kemerataan yang cukup tinggi (H’=1.69, E=0.62, dan D=0.27). Kata kunci: Arachnida, insecta, predator, reptilia, Samia cynthia, Samia cynthia silk moth (Lepidoptera: Saturniidae) is a species of insect that produces silk fibers. Samia silk moth has been domesticated, so it is easy to manage by using feed of cassava (Manihot glaziovii) and castor leaves (Ricinus communis). Predation of S. cynthia silk moths generally occurs in the pre-adult phase. Predators play an important role in biological control agent in the ecosystem. The purpose of this study were to measure diversity and describe the characteristic of predators of S. cynthia. Eggs, larvae, and pupae of Samia were put in a maintenance box and exposed in an open room that accessible for predators. Results showed that 15 species of predator of S. cynthia were found belonging to 3 class, namely Arachnida, Insecta, and Reptilia. The dominant predators of Samia were Dolichoderus thoracicus, Tapinoma melanocephalum, and Iridomyrmex anceps. The diversity of predator of Samia was low with high evenness (H’=1.69, E=0.62, dan D=0.27). Keywords: Arachnida, predatory insect, reptilian, Samia cynthia
Keyword: Arachnida, insecta, predator, reptilia, Samia cynthia

Judul: Perilaku Kawin dan Fekunditas Ngengat Sutera Samia cynthia ricini (Biosduval) (Lepidoptera: Saturniidae)
Abstrak: Samia cynthia ricini (Lepidoptera: Saturniidae) merupakan serangga penghasil sutera komersial, selain ulat sutera domestik Bombyx mori. Perkawinan dan fekunditas merupakan faktor penting yang mempengaruhi kelangsungan hidup, rasio seks, genetika populasi, dan produktivitas ngengat sutera. Tujuan penelitian ini adalah mendeskripsikan perilaku kawin dan mengukur fekunditas ngengat sutera S. cynthia ricini. Dalam penelitian ini diukur bagian tubuh, diamati tahap dan durasi aktivitas perilaku kawin, dan fekunditas ngengat sutera S. cynthia ricini. Hasil pengamatan menunjukkan dimorfisme seksual pada ngengat S. cynthia ricini yaitu imago betina lebih besar ukurannya dibandingkan jantan. Urutan dan durasi dalam perilaku kawin ngengat S. cynthia ricini, meliputi calling (5.00 menit), courtship (2.12 menit), kopulasi (915.62 menit), dan post-kopulasi (oviposisi) (9.12 menit). Peletakkan telur ngengat S. cynthia ricini terjadi selama 4 hari dan oviposisi terbanyak terjadi pada hari pertama. Presentase keberhasilan penetasan telur sebesar 97.81%-99.20%., Samia cynthia ricini (Lepidoptera: Saturniidae) is a commercial silk producing insect other than the domestic Bombyx mori silkworm. Mating and fecundity are important factors influencing survival, sex ratio, population genetics, and silk moth productivity. The purpose of this study were to describe mating behavior and to measure the fecundity of the silk moth S. cynthia ricini. In this study were measured body parts, the stages and activity duration of the mating behavior and the fecundity of S. cynthia ricini. The results showed that the sexual dimorphism was found in S. cynthia ricini that the female body size was bigger than the male. The sequence and duration of S. cynthia ricini mating behavior included calling (5.00 minutes), courtship (2.12 minutes), copulation (915.62 minutes), and postcopulation (oviposition) (9.12 minutes). Oviposition of S. cynthia ricini occurred for 4 days and most oviposition occurred on the first day. The percentage of successfull egg hatching was 97.81% -99.20%.
Keyword: Fecundity, mating, Samia cynthia ricini, silkworms

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.
Keyword: