The chelal moveable digit patterns of seventeen free-living astigmatan mites commonly found in bird nests is decomposed (for the first time) into functional groups using standardised profiles. Contrasts along the mastication surface are used to detect trophic features so as to explain the coexistence of different species in that community. Variation in profiles in general track geometric similarity changes in chelicerae and chelae, except in the moveable digit design transition between Thyreophagus entomophagus TH3 and Lepidoglyphus destructor G6. Full-kerf (Aleuroglyphus ovatus AL2 and Chortoglyphus arcuatus CH1) and particularly thin-kerf (Acarus farris A17) species are found. Both the moveable 'digit tip angle' and the angular bluntness of the anterior region (on which the tip sits, denoted the 'distal digit angle'), mirror digit robustification.Ventral surface intrinsic curvature of the moveable digit appears common across species. Acarus gracilis A4, Glycyphagus domesticus G5 and Lepidoglyphus destructor G6 have more than expected strengthened digit tips compared to other taxa. Rates of this strengthening with chelal occlusive force varies across species. With respect to the whole moveable digit profile a design transition from glycyphagids through acarids to pyroglyphids is found, along with an evolutionary path amongst pest species (Rhizoglyphus robini R1, through Tyrophagus longior T40, to Tyrophagus putrescentiae T13). Acarus gracilis A4 appears unique. In particular Tyrophagus palmarum T17 & T32 and Tyrophagus similis T21 & T44 are indistinguishable from replicates of each other and typify a basal form Tyrophagus longior T40, Tyrophagus putrescentiae T13, Acarus immobilis A1, Tyrolichus casei T62 and Acarus farris A17 are only mildly different from the observed scale of sampling variation of the basal overall profile form in this study Two design groups of ever increasing post-horizontal ramus investment are clear, with the basal rami of Chortoglyphus arcuatus CH1, Thyreophagus entomophagus TH3, Rhizoglyphus robini R1, Glycometrus hugheseae G3 and Dermatophagoides pteronyssinus D3 being taller and sometimes more rounded than those of the distinct group Acarus gracilis A4, Suidasia pontifica S5, Glycyphagus domesticus G5, Lepidoglyphus destructor G6 and Aleuroglyphus ovatus AL2. The bulk of the bird nest astigmatan species have a common profile pattern of apparent asperities on their mastication surface. Although, two species, Rhizoglyphus robini R1 and Chortoglyphus arcuatus CH1, have somewhat exaggerated features on this common 'Bauplan' (perhaps scaled for greater adductive force). Certain species: Acarus immobilis A1, Dermatophagoides pteronyssinus D3, Glycometrus hugheseae G3, Glycyphagus domesticus G5, Lepidoglyphus destructor G6 and Tyrophagus putrescentiae T13, have an individualised distinctly featured mastication surface. These species must each feed differently or on different material in bird nests. Basal ramus and chelal leverage differences are discussed. More work on the ascending ramus and specific dentition in future work is needed to explain certain remaining mite coexistences in this habitat.

Keywords: Acariformes; Chelicerae; Composite tools; Ecomorphology; Morphotypes; Nidicolous habitat; Piercing; Riemannian space; Weaponry.

© 2025. The Author(s).

将十七种常见于鸟类巢穴中的自由生活的食虫螨的螯肢可动指外形模式首次分解为功能组，使用标准化轮廓进行分析。利用咀嚼面的对比来检测生态特征，以便解释该群落中不同物种共存的原因。轮廓变化总体上反映了螯肢和螯爪几何相似性的变化，除了在Thyreophagus entomophagus TH3和Lepidoglyphus destructor G6之间的可动指设计转换外。发现全齿（Aleuroglyphus ovatus AL2 和 Chortoglyphus arcuatus CH1）和特别是薄齿（Acarus farris A17）种类。可动指的“指尖角度”以及前部区域的角钝度（其上放置尖端，标记为“远端手指角度”），反映了指头强化的变化。可动指腹面内曲率在各物种中似乎普遍存在。与其它分类群相比，Acarus gracilis A4、Glycyphagus domesticus G5 和 Lepidoglyphus destructor G6 的指尖加强程度超过预期。不同物种的这种加强随螯爪闭合力的变化而变化。从整个可动指轮廓来看，发现了一条从glycyphagids通过acarids到pyroglyphids的设计转变路径，并且在害虫种类中（Rhizoglyphus robini R1 通过Tyrophagus longior T40 到 Tyrophagus putrescentiae T13）也存在演化路径。Acarus gracilis A4 看起来是独特的。特别是，Tyrophagus palmarum T17 & T32 和 Tyrophagus similis T21 & T44 与各自重复样本无法区分，并代表了原始形式Tyrophagus longior T40、Tyrophagus putrescentiae T12、Acarus immobilis A1、Tyrolichus casei T62和Acarus farris A17仅在观测尺度的采样变异中存在轻微差异。两个设计组越来越大的后水平枝投资清晰可见，Chortoglyphus arcuatus CH1、Thyreophagus entomophagus TH3、Rhizoglyphus robini R1、Glycometrus hugheseae G3 和 Dermatophagoides pteronyssinus D3 的基部枝较高且有时更圆润，而另一组Acarus gracilis A4、Suidasia pontifica S5、Glycyphagus domesticus G5、Lepidoglyphus destructor G6 和 Aleuroglyphus ovatus AL2的则不同。鸟类巢穴中大多数食虫螨种类具有其咀嚼面上明显粗糙的共同轮廓模式，尽管Rhizoglyphus robini R1和Chortoglyphus arcuatus CH1在这一常见“Bauplan”上具有稍微夸大的特征（或许是为了更大的收肌力）。某些物种：Acarus immobilis A1、Dermatophagoides pteronyssinus D3、Glycometrus hugheseae G3、Glycyphagus domesticus G5、Lepidoglyphus destructor G6 和 Tyrophagus putrescentiae T13，在其咀嚼面上具有独特的特征。这些物种在鸟类巢穴中必须以不同的方式进食或食用不同的材料。讨论了基部枝和螯爪杠杆的差异，未来的研究需要更多地关注上升枝和特定齿形，以便解释这种栖息地中某些螨类共存现象。

关键词：Acariformes；螯肢；复合工具；生态形态学；形态类型；巢生环境；穿刺；黎曼空间；武器。