Leaf miners (Acrocercops species) larvae performance on young leaves of Manilkara bidentata

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.

二齿桃榄（Manilkara bidentata）会被一种专性潜叶害虫（specialist leaf miner）——Acrocercops属未定种（Acrocercops sp.，小鳞翅目：细蛾科（Gracillariidae））寄生。单叶片的单个潜道内可发现多头幼虫。本研究旨在明确该潜叶害虫的集群取食效应，因单叶片潜道内的幼虫密度介于1至14头/潜道之间（Angulo-Sandoval 个人观测数据）。这种幼虫密度的差异，为探究幼虫密度对叶片受害程度、幼虫存活率及幼虫生长状况的影响提供了可行条件。带有潜道的叶片面积介于10至224 cm²之间（平均值为85.7 cm²），单叶片内的幼虫数量为1至14头（平均值为5.7头/潜道）。叶片面积与叶片内的幼虫数量无显著相关性。斑状潜道内的幼虫数量与受害组织面积存在显著相关性。植食危害率从单头幼虫时的约10%，随幼虫数量增加升至8头幼虫时的50%。当叶片内幼虫数量超过8头时，植食危害率反而下降。初始幼虫密度对幼虫存活率存在显著影响。单叶片内幼虫数量为1至3头时，幼虫存活率较高（70%）；中等密度区间（4至8头/潜道）的幼虫存活率为50%，而高密度区间（9至14头/潜道）的幼虫存活率仅为22%。尽管高密度区间的幼虫数量会出现下降，但相较于低密度或中等密度区间，最终存活的幼虫总数仍更高。叶片内的幼虫数量与幼虫完成幼虫期所需的发育时长呈线性相关。高密度区间（单潜道幼虫数＞9头）的幼虫发育速度更快，发育时长为3至8天，而低密度区间的幼虫发育时长为5至10天。幼虫羽化时的体长介于8至12 mm之间（平均值为9.27 mm），但幼虫密度对最终幼虫体长无显著影响。存活幼虫总数随初始幼虫数量变化而改变，在初始8头幼虫的潜道中存活总数最高，平均有4.7头幼虫存活；其余所有初始窝卵数对应的存活幼虫数量均少于3头。尽管8头幼虫似乎是最优窝卵数，但大多数雌虫的产卵量较低，单叶片产卵量为4至6头。所有羽化的幼虫均结茧，且其中90%成功羽化为蛾类成虫。