Predation by ground beetles and wolf spiders on herbivorous insects in a maize crop

Ground beetles (Carabidste) and wolf spiders (Lycosidae) are among the domi nant epigeal arthropod predators in arable land. Their predation effect on potential insect populations was examined in a maize field. The abundance a nd effects of ground beetles and wolf spiders were manipulated by removal o r addition within field enclosures during two study periods, midseason and end-season. Both Carabidae and Lycosidae depressed populations of Cicadelli dae and Thysanoptera, and a reduction of Aphididae was indicated in mid-sea son. The results indicated a size-dependent predation effect of Carabidae o n Cicadellidae, the highest predation being on Cicadellidae with a body len gth above 1.1 mm. There was no strong evidence that the predation changed w ith the season. The present study confirmed that ground beetles and wolf sp iders may play an important role in controlling herbivore populations in ag ricultural fields, and revealed their potential to limit Cicadellidae and T hysanoptera in maize field. (C) 1999 Published by Elsevier Science B.V. All rights reserved.