Use of a general model to examine control procedures for a cockroach population

A matrix model for populations is described. The model breaks the population into an appropriate number of stadia to allow for reproductive cycles and includes individual daily survival rates and simple density dependence together with migration. Mortality due to insecticidal treatments may be applied on specified days to simulate space spraying while residual insecticides may be simulated with constant or declining effect. The use of the model is exemplified using a simulated population of Blattella germanica with various treatment regimes. This simulation emphasised the importance of immigration.     

Conservation of Glycerolated Cultures of Ochromonas danica and O. malhamensis at −10 C

SYNOPSIS. Ochromonas danica in a complex natural growth medium dies at 6–10 C in 4 days; O. malhamensis in ∼2 days. O. danica grown in the medium supplemented with 4.0% glycerol survived at −10±2 C for 35 days, and with 8% glycerol 29 days. O. malhamensis lasted only to 5 days in these media supplemented with 4% glycerol. Ethylene glycol and dimethylsulfoxide were too toxic to be effective. Difficulties in freeze-preservation of certain other phagocytic cells, notably blood granulocytes having comparatively simple flexuous outer membranes, add interest to use of O. danica and O. malhamensis as test organisms for preservation methods, especially in the convenient, inexpensive -10 to -20 C range. Biphasic media with an overlay of distilled water serve for conservation at room temperature. Problems of mutational erosion of these photosynthetic phagotrophs are discussed.