<b>Scrutinizing </b><b><i>Acalitus simplex </i></b><b>Flechtmann et Etienne (Eriophyidae): an eriophyoid mite associated with </b><b><i>Ruellia</i></b><b> spp.</b><b><i> </i></b><b>(</b><b>Acanthaceae</b><b>)</b>

<i>Acalitus simplex</i> is an erinose eriophyoid mite that feeds exclusively on plants in the genus <i>Ruellia,</i> which are frequently sold as ornamentals for landscape plantings. This study presents a comprehensive examination of <i>A. simplex</i> collected from Anguilla, Brazil, Dominican Republic, Florida, and Hawaii through sequencing of the mitochondrial cytochrome oxidase I gene (COI), coupled with morphological examination by several microscopy techniques. The collected <i>A. simplex</i> specimens were similar in morphology across geographic locations and populations clustered together in a phylogenetic analysis based on COI sequences. In addition to <i>Ruellia simplex</i>, new host plant associations are reported in Florida, including <i>R. blechum</i>, <i>R. squarrosa</i> and <i>R. caroliniensis</i>. We defined the different erineum stages, determined the number of days after infestation on an uninfested plant required for erinea development, and estimated population densities in each erineum stage. Four erineum stages were observed on <i>R. simplex</i> - hyaline (stage 1), white (stage 2), purple (stage 3) and beige (stage 4). At 25 ± 2 ^oC, 12:12/L:D and 50 ± 10% RH, the purple stage did not develop and the duration of the hyaline, white and beige erinea was 12.4 ± 0.7 (mean ± SE), 44.4 ± 1.3, and 20.5 ± 0.9 days, respectively. Population densities varied significantly across the erineum stages, with most individuals in the white and purple stages and fewer in the hyaline and beige stages. This study improves our understanding of interactions between <i>A. simplex</i> and <i>R. simplex</i>, aiding the development of IPM strategies to mitigate this mite.简单刺足瘿螨（Acalitus simplex）是一种专性寄生于芦莉草属（Ruellia）植物的毛毡状瘿螨，该属植物常作为景观观赏植物被售卖。本研究对采自安圭拉、巴西、多米尼加共和国、佛罗里达及夏威夷的简单刺足瘿螨样本开展了综合分析：通过线粒体细胞色素C氧化酶亚基I基因（COI）测序，并结合多种显微技术完成形态学检测。不同地理来源的简单刺足瘿螨样本形态特征无显著差异，基于COI序列的系统发育分析显示，各地理种群聚为单一分支。除芦莉草（Ruellia simplex）外，本研究在佛罗里达地区报道了该螨的3种新寄主植物，分别为布吕赫芦莉草（R. blechum）、粗茎芦莉草（R. squarrosa）和卡罗莱纳芦莉草（R. caroliniensis）。本研究明确了该螨诱导形成的毛毡瘿的不同发育阶段，测定了未受侵染植株被侵染后毛毡瘿发育所需的时长，并估算了各发育阶段的种群密度。在芦莉草上共观察到4个毛毡瘿发育阶段：透明期（阶段1）、白色期（阶段2）、紫色期（阶段3）及米色期（阶段4）。在25±2℃、光暗周期12:12、相对湿度50±10%的实验条件下，紫色期毛毡瘿未出现发育；透明期、白色期及米色期毛毡瘿的持续时长分别为12.4±0.7（平均值±标准误）、44.4±1.3及20.5±0.9天。不同毛毡瘿发育阶段的种群密度存在显著差异，多数螨个体集中于白色期与紫色期，透明期及米色期的个体数量相对较少。本研究加深了学界对简单刺足瘿螨与芦莉草之间互作关系的认知，可为制定该螨的综合害虫治理（IPM）策略提供理论支撑。