Judul: Kelimpahan, Biologi, dan Kemampuan Pemangsaan Oligota sp. (Coleoptera: Staphylinidae), Kumbang Predator Tungau pada Tanaman Ubikayu
Abstrak: Mites infestation is one of the main problem in many agricultural commodities. One of the best methods to control mites infestation is biological control using insect predators. The objective of this study is to know the abundance, biology, and predation ability of mites-predatory beetle, Oligota sp. on cassava. Surveys were conducted in cassava plantation around Bogor to know the abundance of Oligota sp. Oligota sp. collected from the field were reared in the laboratory to observe its biology. Experiment to know the predation ability of Oligota sp. was conducted using 3rd stage larvae, with 5, 10, 15, 20, and 25 adult mites as preys. Observations were carried out 3, 6 and 24 hours after treatment. The developmental time of male and female were 15.047 and 16.097 days, respectively. The longevity of male and female were 20.974 and 21.677 days respectively. Female laid 22.923 eggs in 14.154 days. The 3rd stage larva of Oligota sp. consumed 18 adult mites for 24 hours.
Keyword: Oligota sp., predation, biology, abundance

Judul: Biology and Life table of the Beetle Cryptolaemus montrouzieri (Mulsant) (Coleoptera: Coccinellidae) on Cassava  Mealybug
Abstrak: Indonesia merupakan produsen singkong (Manihot esculenta) terbesar keempat di dunia setelah Brazil, Nigeria, dan Thailand. Kutu putih Phenacoccus manihoti merupakan hama paling berbahaya pada singkong yang berpotensi menimbulkan serangan berat. P. manihoti mendapat nutrisi dengan cara menghisap cairan dari tanaman dan menyerang bagian pucuk tanaman. Cryptolaemus montrouzieri diketahui merupakan musuh alami yang sangat efisien memangsa kutu putih dalam jumlah banyak. Penelitian dilakukan di laboratorium dengan tujuan untuk mengetahui (1) masa perkembangan pradewasa, lama hidup imago dan keperidian, (2) parameter neraca hayati predator C. montrouzieri pada tanaman singkong. Hasil penelitian menunjukkan periode inkubasi telur 4,01 hari. Rata-rata perkembangan masing-masing larva instar 1, 2, 3 dan 4 berturut-turut adalah 3,28; 4,15; 4,67 dan 4,79 hari. Prapupa dan pupa masing-masing berlangsung 1,41 hari dan 6,26 hari. Total masa perkembangan masing-masing pradewasa jantan 28,91 hari dan betina 28,57 hari. Masa hidup imago jantan adalah 26,12 hari, sedangkan betina 25,45 hari. Jumlah telur yang diletakkan oleh seekor betina rata-rata 168 butir. Studi neraca hayati menunjukkan laju reproduksi kotor (GRR) 61,843 betina per generasi. Laju reproduksi bersih (R0) 37,745 betina per betina per generasi. Laju pertambahan instrinsik (r) 0,072 betina per betina per hari. Rataan lama generasi (T) 50,145 hari. Waktu yang dibutuhkan populasi untuk berlipat ganda (DT) adalah 9,572 hari., Indonesia is the fourth largest cassava (Manihot esculenta) producer in the world after Brazil, Nigeria, and Thailand. Mealybug Phenacoccus manihoti is the most dangerous pest in cassava that has the potential to cause severe damage. P. manihoti gets nutrients by sucking fluid from the plant and attacking the shoots of the plant. Cryptolaemus montrouzieri is known to be a natural enemy that is very efficient in preying on mealybugs. The research was conducted in the laboratory with the aim to determine (1) the period of preadult development, adult life span and pupilage, (2) life table parameters of C. montrouzieri preys on mealybug. The results showed that the egg incubation period was 4.01 days. Mean developmental periods for 1st, 2nd, 3rd, and 4th instar larvae were 3.28; 4.15; 4.67 and 4.79 days, respectively. Prepupae and pupae lasted for 1.43 days and 6.26 days, respectively. The total developmental period of male preadult was 28.91 days and female preadults 28.57 days, respectively. The life span of the adult was 26.12 days for males and 25.45 days for females. The number of eggs laid by a female averaged 168. The life table study showed the gross reproductive rate (GRR) of C. montrouzieri was 61.843 females per generation. The net reproductive rate (R0) was 37.745 females per female per generation. The intrinsic rate of increase (r) of C. montrouzieri was 0.072 females per female per day. Average generation length (T) of C. montrouzieri was 50.145 days. The time taken for the population to double (DT) was 9.572 days.
Keyword: Demographic parameter, life cycle, 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.
Keyword: