Journal of Insect Behavior, Vol. 3, No. 6, 1990 Variation in Foraging Investment During the Intermolt Interval and Before Egg-Laying in the Spider Nephila clavipes (Araneae: Araneidae) Linden E. Higgins l'z Accepted December 5, 1989; revised June 4, 1990 Repeated observations were made of marked, free-living females in three dis- junct populations of the orb-weaving spider Nephila clavipes, recording orb size and structure and barrier web complexity. These longitudinal studies revealed regular patterns of variation in orb size associated with the molting cycle and cycle of egg maturation. Juveniles maintained in an insectary under a controlled feeding regime exhibited similar variation in orb size. All spiders ceased orb renewal prior to molting and the majority replaced the viscid orb with a nonviscid platform prior to molting. Differences among the populations in molting web structure are discussed in light of differences in the physical and biological environments. Cessation of orb renewal corresponded tempo- rally with reported physiological changes associated with the molt cycle and possibly reflect changes in resource partitioning between growth and foraging during the molt cycle. KEY WORDS: Araneidae; foraging; molt cycle; web structure. INTRODUCTION The foraging effort of an individual organism is not constant. Energetic require- ments and therefore the foraging effort of the organism are expected to change allometrically (Phillipson, 1981; Calow and Townsend, 1981). Similarly, at different stages in the life history resources will be shifted from foraging to other efforts, such as territoriality, courtship, and reproduction (Pianka, 1981; t Department of Zoology, University of Texas at Austin, Austin, Texas 78712. ZCurrent address: Centro de Ecologia, UNAM, Apt, Post. 70-275, Ciudad Universitaria, C.P. 04510, M6xieo. 773 0892-7553/90/1100-0773506.00/0 9 1990 Plenum Publishing Corporation