OVIPOSITION PREFERENCES OF CULEX-PIPIENS AND CULEX RESTUANS FOR INFUSION-BAITED TRAPS

The number of egg rafts oviposited by Culex pipiens and Culex restuans in infusion-baited ovitraps varied with the type of infusion substrat e, infusion age, method of infusion preparation, and calendar date. In one or more tests, more Culex egg rafts were collected from water inf used with Kentucky bluegrass sod, mixed grass clippings, straw, or a c ommercial rabbit chow than from a water control. Infusions prepared wi th oak leaves, maple leaves, and sod soil were ineffective as Culex ov iposition attractants; however, alfalfa infusions ranged from marginal ly effective to unattractive. Rabbit chow infusions required one or mo re reinfusions before becoming active oviposition lures when prepared in unconditioned (unused) ovitraps. Infusions prepared in conditioned ovitraps (those that had previously contained the same type of infusio n) had shorter delay periods. Effective oviposition lures for Culex sp ecies included continuous infusions, such as sod and sod grass, and th ose in which the substrate was infused in the water for only a brief p eriod (24-48 h), such as infusions of rabbit chow and mixed grass clip pings. The percentage of egg rafts from Cx. restuans was usually great er in sod and grass infusions than in rabbit chow infusions, whereas C x. pipiens showed a slight preference for rabbit chow infusions over s od and grass infusions. The temporal shift in relative oviposition act ivity of the 2 Culex species (cross-over) varied from year to year and between sites in one year.