Microstructure and formation of protective coverings in some plant-parasitic microarthropods

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1. Scale insects. The male and female tests of some species of the family Diaspididae were observed in a scanning electron microscope, and their microstructures were compared with reference to corresponding secretory organs. Highly magnified tests are mainly composed of wax filaments, but not uniform in structure among the species observed. An evolutionary trend of the test from a fluffy mass of filaments to a thin, tight and broad covering is recognized, and in parallel in different groups of the family. Advanced types of tests are made by oscillatory or nearly rotatory movements of the insects, but in the Diaspidini the male test shows no trace of such movements. It seems that in the Aspidiotinae the movement takes place at an early stage of the evolutionary course. Another factor in forming thin and thick tests is a glutinous substance discharged from the anus. This substance is resistant against some lipid solvents. Thus, the tests of advanced diaspidids are effective protecting coverings both in structure and in substance.2. Spider mites. A new method of preparing specimens of Tetranychidae for scanning electron microscopy (SEM) was developed. By the use of this method material can be prepared without shrinking. Material was collected mainly from broad-leaved evergreen trees and perennial grasses during May to June, 1989, in Kyusyu and Okinawa, and many spider mites including more than 10 species of 5 genera were found in the collection. Their life types were determined. They were prepared for SEM and their microstructures were observed. On the basis of SEM observations, two species which have been confused under the name Schizotetranychus celarius (Banks) are newly recognized and described. It has also been found that males of a spider mite species belonging to the "woven nest" life type are very antagonistic in behavior within their nests. Cryo-system SEM observations have demonstrated that this is due to cannibalism among them.