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: Karakteristik Morfologi Ngengat Sutra Samia cynthia ricini (Lepidoptera : Saturniidae) pada Pemberian Pakan Larva Berbeda
Abstrak: Ngengat Samia cynthia ricini (Lepidoptera: Saturniidae) merupakan serangga penghasil serat sutra komersial yang telah banyak didomestikasi. Kualitas daun pakan mempengaruhi pertumbuhan, mutu kokon dan serat yang dihasilkan. Penelitian ini bertujuan mengkaji karakteristik morfologi S. c. ricini fase larva, pupa, dan imago dengan pemberian tiga pakan larva berbeda. Dalam penelitian ini digunakan tiga jenis pakan larva, yaitu daun singkong karet (Manihot glaziovii), daun jarak kepyar (Ricinus communis), dan daun pepaya jepang (Cnidoscolus aconitifolius). Pengamatan yang meliputi ukuran, bobot, warna dan durasi dilakukan pada setiap fase pertumbuhan. Hasil penelitian menunjukkan pemberian pakan daun jarak kepyar menghasilkan pertumbuhan larva S. c. ricini paling baik berdasarkan karakteristik panjang, lebar dan bobot larva. Terdapat enam variasi warna dan corak larva S. c. ricini yaitu hijau-zebra, hijau, kuning-zebra, kuning, putih-zebra, dan putih. Persentase kokon yang terbentuk paling tinggi terjadi pada pemberian pakan jarak kepyar. Ukuran imago tidak berbeda nyata pada pemberian pakan daun singkong karet dan jarak kepyar. Siklus hidup ngengat S. c. ricini dengan pemberian pakan daun jarak kepyar lebih singkat dua hari dibandingkan dengan pemberian pakan daun singkong karet. Pada pemberian pakan daun pepaya jepang, mortalitas larva instar 5 mencapai 100%., The silkworm Samia cynthia ricini (Lepidoptera: Saturniidae) is a commercial silk fiber-producing insect that has been widely domesticated. Leaf quality as feed will affects growth, cocoon quality, and fiber quality produced of silkworm. This study aims to examine the morphological characteristics of S. c. ricini at the larvae, pupa, and imago phase by three different feeds. In this study, three species of larvae fed were used as feed of larvae, namely cassava leaves (Manihot glaziovii), castor leaves (Ricinus communis), and chaya leaves (Cnidoscolus aconitifolius). Observations including size, weight, color and duration were carried out at each growth phase. The results showed that castor leaves result the best growth of S. c. ricini based on the ratio of length, width, and weight of larvae. There are six variations in color and larvae patterns of S. c. ricini, namely green-zebra, green, yellow-zebra, yellow, white-zebra, and white. The highest percentage of cocoons formed occured in larvae fed by castor leaves. The body size of the imago did not differ on the larvae fed by cassava and castor leaves. The duration of the life cycle of the S. c. ricini larvae fed by castor leaves was two days shorter compared to cassava leaves. Giving of chaya leaves results the mortality of instar 5 larvae reaches 100%.
Keyword: Lepidoptera, life cycle, morphology, Samia cynthia ricini

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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