The spatial arrangement of needle fascicles on slash pine shoots consisted of 21 fascicles in a spiral that turned around the shoot eight times before repeating itself. This cyclic unit was used to map the distribution of narrow, non-egg-bearing slits (“probes”) and egg-bearing pockets made by femaleNeodiprion merkeliRoss in the foliage of one large, heavily infested shoot. Females exhibited a strong apical response in reference to growth flushes on the shoot and a 5:1 preference for accepting the needles of two-needle rather than three-needle fascicles for oviposition. In 47 lightly infested shoots, the mean number of eggs laid per needle was 30% greater in needles from two-needle fascicles but increased with increasing needle width for two- and three-needle fascicles. The incidence of single probes unaccompanied by oviposition in the same needle was 28 times higher in needles from three than two-needle fascicles, a difference attributed to the relatively narrow flat-side width of needles available for oviposition in some three-needle fascicles.