Tetranychus urticae Koch, 1836 Knob of male aedeagus always small, axis of knob parallel to shaft axis or forms a small angle with shaft axis; dorsal margin of knob and development of anterior and posterior projections may vary, but in most case they are similar (Figure E); male empodium I with strong medio-dorsal spur; about length of 2 proximoventral spurs; empodium II consists of 3 pairs of proximoventral hairs and a strong mediodorsal spur. Specimens examined: From many hosts all over Kenya: Lycopersicon esculentum (Solanaceae), Phaseolus vulgaris L. (Fabaceae), Zea mays L. (Poaceae), Amaranthus hybridus L. (Amaranthaceae)., Carica papaya (Caricaceae), Galinsoga parviflora (Asteraceae)., Desmodium sp. (Fabaceae), Bidens pilosa (Asteraceae ) , Cucurbita pepo (Cucurbitaceae), Citrullus lanatus (Cucurbitaceae), Lactuca sativa (Asteraceae), Rosa sp. (Rosaceae), Passiflora edulis (Passifloraceae), Helianthus annuus (Asteraceae), Euphorbia sp. (Euphorbiaceae), Tradescantia fluminensis (Commelinaceae), Citrus sp. (Rutaceae), Brassica sp. (Brassicaceae), Lantana camara (Verbenaceae), Datura stramonium (Solanaceae), Pisum sativum (Fabaceae), Dianthus caryophyllus (Caryophyllaceae). Remark: Tetranychus urticae was first described on Glyine max and Urtica sp from Germany (Koch, 1836). It is one of the most cosmopolitan spider mite species with worldwide distribution and a wide host range. It is considered a pest of many crops and is the most studied spider mite species with a high rate of pesticide resistance reported on this species by many authors. In Kenya, it is a major menace in cut flower production especially in Rosa sp. Its first record in Kenya was on Allium ampeloprasum (Alliaceae) from Machakos district and on Lathyrus odorata (Fabaceae) from Nairobi (Baker and Pritchard, 1960).

Published as part of Toroitich, Faith J., Ueckermann, Edward A., Theron, Pieter D. & Knapp, Markus, 2009, The tetranychid mites (Acari: Tetranychidae) of Kenya and a redescription of the species Peltanobia erasmusi Meyer (Acari: Tetranychidae) based on males, pp. 33-47 in Zootaxa 2176 on pages 45-46, DOI: 10.5281/zenodo.189364