Advisor: Harald Krenn
Master's Defensio
Wednesday, September 11th, 2024, 9:30 am CET
SR 1.2, UBB
Djerassiplatz 1, 1030 Vienna
Abstract
This study investigated the biting-chewing mouthparts and the feeding behavior of the herbivorous, neotropical stick-insect Peruphasma schultei Conle & Hennemann, 2005 (Phasmatodea). Emphasis was laid on the comparison of the size and morphology of the mandible in the various developmental stages and adults. In addition, the bite marks on leaves were analyzed and compared in all five nymphal stages and imagines. About 60 female individuals of Peruphasma schultei were reared in several plastic boxes, about ten individuals per developmental stage. They were fed with Ligustrum vulgare and were held under humid conditions at room temperature in the lab. The morphological and biometrical studies were done using light microscopy and scanning electron microscopy. The bite marks of the various stages were studied on dried pressed leaves. The feeding behavior was filmed using a cell phone tool.
The results show that the size of the mandibles increases from stage to stage but the morphology is more or less uniform. In all investigated individuals the left mandible overlaps the right one. The prognathous orientation of the mandibles is more pronounced in the early nymphal stages. The feeding behavior is similar in all developmental stages. The leave is held between the mouthparts and biting movement starts from dorsal and proceeds to ventral. Then the head is lifted rapidly and next biting cycle starts from above. The maxillary palpi and labial palpi keep in contact with the leaf. The bit marks become bigger in later stages and adults compared to early nymphs but they keep the same pattern and shape.
This study provides first comparative data of all developmental stages of herbivorous insects. The mandible morphology and bite marks of Peruphasma schultei were compared with other species of Phasmatodea and other herbivorous, omnivorous and predatory Polyneoptera as well as with similar studies in Coleoptera and caterpillars.
