短毛切梢小蠹成虫口器感器的扫描电镜观察

Ultramorphological observations of the mouthpart sensilla of adult Tomicus brevipilosus(Coleoptera:Scolytinae)

口器是昆虫近距离感知的重要器官,通过环境扫描电镜对发生于云南地区的短毛切梢小蠹成虫口器上的感器进行观察,并作了详细描述。短毛切梢小蠹口器由1个上唇,1对上颚、1对下颚、1个下唇和1个舌组成,共有6类12种感器,分别为毛形感器(2亚型)、刺形感器(3亚型)、锥形感器(2亚型)、末梢锥形感器(3亚型)、腔锥形感器和指形感器。毛形感器数量最多,分布于上颚、内颚叶、外颚叶上部及上唇;刺形感器则位于茎节、内颚叶、下唇、下颚须与下唇须的节间处;锥形感器1仅分布于下唇内侧,而锥形感器2和末梢锥形感器则呈聚集分布于下颚须和下唇须的端部,且感器末端均有微孔;腔锥形感器和指形感器仅着生于下颚须第3节侧面,但没有感器分布于舌表面。口器感器的类型、数量和分布均没有性二型现象,但末梢锥形感器3和指形感器的数量存在种内变异,前者有9~13个,后者有4~6个。研究结果将为探讨短毛切梢小蠹的寄主选择、取食与求偶行为提供参考。

Insect mouthparts are indispensable sensory organs that detect environmental cues over a short distance. In this study, using environmental scanning electron microscopy, we observed the types, distributions, and numbers of various sensilla occurring on the mouthparts of adult Tomicus brevipilosus, which is one of the most important coniferophagous beetles in Yunnan province. The mouthparts of adult Tomicus brevipilosus consist of one labrum, a pair of mandibles, a pair of maxillae, one labium, and a hypopharynx. There are six types of sensilla on the mouthparts: sensilla trichodea(2 subtypes), sensilla chaetica(3 subtypes), sensilla basiconica(2 subtypes), sensilla twig basiconica(3 subtypes), sensilla coeloconica, and sensilla digitiformia. Sensilla trichodea are the most abundant and generally located on the mandibles, lacinea, upper galea, and labrum. Sensilla chaetica are present on the stipes, lacinea, intersegmental joints of maxillary and labial palpus. Sensilla basiconica type Ⅰ is found only on the internal view of the labium. Sensilla basiconica type Ⅱ and sensilla twig basiconica are terminal pores and show an aggregated distribution on the terminal apex of the maxillary and labial palps, respectively. Sensilla coeloconica and sensilla digitiformia are located only on the lateral view of the third subsegment of the maxillary palpus. No sensilla were observed on the surface of the hypopharynx. No sexual dimorphism was observed in sensilla types, numbers, and distribution between female and male adult T. brevipilosus. However, sensilla twig basiconica type Ⅲ and sensilla digitiformia showed a number variation within species. The former included 9-13 sensilla at the site of distribution, whereas the latter had 4-6. This study provides a reference for further exploration of host selection, feeding, and mate recognition of the pest Tomicus brevipilosus.