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<p><i>Dastarcus helophoroides</i> is a key parasitoid against cerambycid pests, with its larval stage being pivotal for short-range host search, location, and parasitism. However, ecological traits and morphological shifts during parasitism remain poorly documented. This study employed scanning electron microscopy (SEM) to characterize morphological features of first-instar larvae and ontogenetic changes during parasitism, while assessing survival and locomotory capacity under environmental stressors. Results confirm larval hypermetamorphic development: the planidial first&#xa0;instar exhibits a sensilla-rich head, developed prognathous mouthparts with hooked/hollow/sharp mandibles, and robust thoracic legs bearing serrated claws, whereas later vermiform instars show leg degeneration and retracted mouthparts. At 25&#xa0;°C, first-instar larvae survive only 2–3&#xa0;days with significantly reduced locomotion after one day, indicating high host-selection pressure. This work establishes: (1) hypermetamorphosis in&#xa0;<i>D. helophoroides</i>, (2) identification of the planidial first&#xa0;instar as the key parasitic stage, (3) quantification of temporal constraints, and (4) a morphological foundation for studying morpho-behavioral co-adaptation in parasitism mechanisms.</p>

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Developmental morphology reveals the key parasitic role of the first-instar larva in the hypermetamorphosis of Dastarcus helophoroides (Coleoptera: Bothrideridae)

  • 期刊论文

  • 发表日期：

    2026年3月16日

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  • Yifan Zhang,
  • Ke Wei,
  • Xueting Yang,
  • Cuicui Geng,
  • Shangkun Gao

摘要

Dastarcus helophoroides is a key parasitoid against cerambycid pests, with its larval stage being pivotal for short-range host search, location, and parasitism. However, ecological traits and morphological shifts during parasitism remain poorly documented. This study employed scanning electron microscopy (SEM) to characterize morphological features of first-instar larvae and ontogenetic changes during parasitism, while assessing survival and locomotory capacity under environmental stressors. Results confirm larval hypermetamorphic development: the planidial first instar exhibits a sensilla-rich head, developed prognathous mouthparts with hooked/hollow/sharp mandibles, and robust thoracic legs bearing serrated claws, whereas later vermiform instars show leg degeneration and retracted mouthparts. At 25 °C, first-instar larvae survive only 2–3 days with significantly reduced locomotion after one day, indicating high host-selection pressure. This work establishes: (1) hypermetamorphosis in D. helophoroides, (2) identification of the planidial first instar as the key parasitic stage, (3) quantification of temporal constraints, and (4) a morphological foundation for studying morpho-behavioral co-adaptation in parasitism mechanisms.