Monochamus titillator Oviposition and Intraspecific Competition in Shortleaf Pine Bolts

Monochamus titillator (Coleoptera: Cerambycidae) feed on trees in the family Pinaceae as adults and larvae. Adults feed on healthy twigs and branches and oviposit on stressed, dead, or dying trees. Prior to oviposition, females construct pits on the bark surface using their mandibles. The number of eggs laid beneath bark, where oviposition pits have been constructed, varies greatly. Developmental time and adult body size also vary greatly. I investigated oviposition and intraspecific competition with the goal of determining the degree to which various insect densities and oviposition times impact the following: 1) oviposition pit construction; 2) egg deposition; 3) emergence, 4) and adult body size. Females constructed 463 oviposition pits and laid 1002 eggs on 26 bolts. The average number of pits per bolt was 17.8 and the average number of eggs per bolt was 38.54. The average number of eggs per pit was 2.16 and differed significantly between our treatment combinations (P=0.0132). Significant differences were detected between our treatment combinations for the number of pits constructed (P=0.0011*) and eggs deposited (P=0.0327*). There was a positive correlation between the number of pits per bolt and the number of eggs per bolt (P=-.0001*, R 2=0.691). Emergence occurred in 49 out 60 bolts and 222 M. titillator emerged in total. The average number to emerge was 3.9 M. titillator per bolt and the mean number for emergence differed significantly between our treatment combinations (P<0.0001). A significant and positive correlation was detected between the mean number of pits per bolt and the mean number for emergence (P>0.0001, R2=0.448). It took an average of 96 days for larvae to emerge. These data, when taken together suggest that density dependent responses were detected and can be attributed to intraspecific competition.