Manilkara bidentata is attacked by a specialist leaf miner(Acrocercops sp.(microlepidoptera:gracillariidae). More than one larvae can be found per mine within a leaf. The purposes of this study is to determine the effect of group feeding for this species since larval density within a leaf vary from 1-14 larvae per mine (Angulo-Sandoval personal observation). This variation allows to determine the effect of larval density on the amount of leaf damage, larval survivorship and larval growth. Leaves with mines varied in area from 10 to 224 cm2 (mean = 85.7 cm2) and the number of larvae per leaf ranged from 1 to 14 (mean = 5.7 larvae/mine). There was no relation between the size of the leaf and the number of larvae found within the leaf.
There was a relationship between the number of larvae in a blotch mine and amount of damaged tissue. Herbivory increases from approximately 10% for one larva per leaf to 50% in leaves with eight larvae. In leaves with more than eight larvae, herbivory decreased . There was an effect of initial larval density on percent larval survivorship.Survivorship was high (70%) in leaves with one to three larvae. In intermediate density (4-8 larvae per mine) 50% of larvae survived and in high densities (9 - 14 larvae per mine), only 22% survived. Even though there was a decrease in larvae number in high densities, the final number of larvae remained higher, compared with low or intermediate densities. A linear relationship was found between number of larvae present in the leaf and the time it took the larvae to complete their larval stage. Larvae in high density (> 9 larvae per mine) tended to develop faster (3-8 days) than larvae in low densities (5 - 10 days). Larval size upon emergence ranged from 8 to 12 mm (mean= 9.27) but there was no effect of larval density on the final larval size. The total number of surviving larvae varied according to the initial larval number and was highest in mines with eight individuals of which on average 4.7 survived. The number of surviving larvae was less than three for all other clutch sizes. Even though eight larvae appears to be the optimum clutch size, most females produced smaller clutches (4- 6 larvae per leaf).All larvae that emerged built a cocoon and 90% emerged as butterflies.