| Summary: | 碩士 === 國立中興大學 === 植物學系 === 88 === Most grasshoppers are phytophagous insects. The community structure of grasshoppers is influenced by vegetation type. In Guandaushi forest ecosystem, grasshoppers include forest-habitated and ground-habitated types. We investigated the phytophagy of grasshoppers belonging to superfamilies of Acridoidea and Eumastacoidea at Guandaushi forest. The investigations involved measurment of vegetational changes over a 19-month period, field observations of feeding events of grasshoppers, laboratory studies of food preference, and observations of mandibular morphology.
There were tentatively 20 species of grasshoppers belonging to 6 families at Guandaushi. Three species are still under further identification. The range of food plants selected by grasshoppers varied from species to species. Based on field observations, they were mostly polyphagy or oligophagy. There was no evidence to suggest that changes in vegetation were directly responsible for changing in grasshopper population density. Phytophagous grasshoppers have structural adaptations of mandibles to different types of food plants. Based on SEM observations, the mandibles of them could be grouped into three types: (1)type Ⅰ, the incisor surface consists of sharp dentes, and the molar area is a deep, central concavity surrounded by very short ridges; (2)type Ⅱ, the incisor surface is somewhat a smooth cutting edge without dentes, and the molar surface is long parallel grinding ridges without central concavity; (3)type Ⅲ: the incisor has blunt dentes, and the molar area consists of ridges with central concavity shorter than type Ⅰ. Grasshoppers with type Ⅰ mandibles feed primarily on forbs, and occasionally feed on succulent grasses. Those with type Ⅱ mandibles are grasses feeders. A few species at times feed on forbs, but in low quantity. Those with type Ⅲ mandibles are mix feeders that feed freely from forbs and grasses. Mandibular structure could refer to the main type of food plant consumed by grasshoppers. Their food preferences are differ from species to species, we could ascertain their food plants species by field observations or laboratory studies.
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