The chromosome numbers and types of parthenogenesis have been assessed for 19 species of 6 different genera of the Tenuipalpidae. The modal number of n = 2 is found to occur in species of the genera Aegyptobia, Cenopalpus, Brevipalpus, Dolichotetranychus and Raoiella. The bisexual species examined exhibit haplo-diploidy (with n = 2 and 2n = 4) as a result of arrhenotokous parthenogenesis. Thelytokous parthenogenesis with female diploidy is found in Aegyptobia vannus (2n = 4), Aegyptobia thujae (2n = 4) and in Tenuipalpus spec. (2n = 6). Thelytoky with female haploidy exists in Brevipalpus obovatus and B. phoenicus, both with n=2.

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Rate of development and reproduction of Orius vicinus was measured on different sorts of animal prey and on Vicia fabae pollen. Several phytophagous and predacious mites proved to be good prey species for the predator, but some small insects, such as Typhlocyba sp. and Aphis pomi were less suitable. Reproduction on a diet of Vicia fabae pollen was distinctly lower than on animal prey. Electrophoretic analysis of gut contents of field collected predators showed that these fed almost exclusively on the rust mite Aculus schlechtendali. In a number of instances, Typhlodromus pyri could be identified as the prey of O. vicinus. The predator was only observed on trees of the apple cultivar Beauty of Boskoop. The role of O. vicinus in the suppression of phytophagous mite populations is discussed. Zusammenfassung Zur Bedeutung von Orius vicinus Ribaut (Het., Anthocoridae) als Räuber phytophag und räuberisch lebender Milben in Obstgärten der Niederlande Es wurde die Entwicklungs‐ und Vermehrungsrate von Orius vicinus bei der Ernährung mit verschiedenen Beutetieren und mit Vicia fabae‐Pollen bestimmt. Mehrere phytophage und räuberische Milben erwiesen sich als geeignete Beutetiere für O. vicinus, jedoch waren einige kleine Insekten, wie Typhlocyba sp. und Aphis pomi, weniger gut geeignet. Bei Fütterung mit Vicia fabae‐Vollen war die Reproduktionsrate deutlich geringer als bei tierischer Ernährung. Eine Analyse des Darminhalts von im Freiland gesammelten Tieren mit Hilfe der Elektrophorese ergab, daß O. vicinus sich fast ausschließlich von der Rostmilbe Aculus schlechtendali ernährt. In einigen Fällen konnte Typhlodromus pyri als Beutetier festgestellt werden. O. vicinus wurde nur auf Apfelbäumen der Züchtung “Beauty of Boskoop” gefunden. Die Bedeutung von O. vicinus zur Populationsregulation phytophager Milben wird diskutiert.

Examination of recently collected material of the mailed catfish genus Lasiancistrus Regan, 1904, from French Guiana and Surinam revealed L. niger (Norman, 1926), and two new species: L. brevispinis and L. longispinis. The three species are described and figured. Lasiancistrus is compared with 13 other genera, forming the tribe Ancistrini of the subfamily Ancistrinae.

The chromosome numbers have been assessed for 31 bisexual species of 14 different genera of the Tetranychidae, bringing the total of karyotyped species in this family to 109. The taxonomic significance of karyotype information is discussed. A haploid number of n=5 occurs in Neotrichobia arizonensis, Eotetranychus fremonti and E. gambelii ; of n=4 in Marainobia spec.