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Parasite dilution occurs in varied systems, via multiple potential mechanisms. We used laboratory manipulation and field survey to test for invader-induced parasite dilution via two specific mechanisms: host-host competition and encounter reduction. In the laboratory, single Aedes triseriatus larvae were exposed to one of 8 combinations of: +/- parasitic Ascogregarina barretti, +/-1 cohabiting Aedes albopictus larva during parasite exposure, and +/-1 cohabiting A. albopictus larva after infectious parasite removal. Larval infection intensity (predicted to decrease via dilution by encounter reduction) was not significantly affected by A. albopictus. Adult infection prevalence and intensity (predicted to decrease via dilution by host-host competition) were significantly greater with A. albopictus, suggesting parasite amplification by interspecific competition, an effect potentially mediated by competition increasing A. triseriatus development time. In the field, we tested for effects of potential dilution host abundances on prevalence and abundance of A. barretti in A. triseriatus larvae. Piece-wise path analysis yielded no evidence of host-host competition impacting parasitism in the field, but instead indicated a significant direct negative effect of Aedes spp. abundance on parasite abundance in A. triseriatus, which is consistent with dilution via encounter reduction in the field, but only in treeholes, not in man-made containers. Our results are consistent with the hypothesis that a non-competent invader can alter the native host/parasite relationship, but our laboratory and field data yield differing results. This difference is likely due to laboratory experiment testing for per capita effects of dilution hosts on parasitism, but the field analysis testing for effects of dilution host abundance on parasitism. Individually, host-host competition with the invader amplifies, rather than dilutes, parasite success. In contrast, our path analysis is consistent with the hypothesis that dilution of parasitism results from increased abundance of noncompetent hosts in the field.寄生虫稀释效应可通过多种潜在机制在多样生态系统中发生。本研究通过实验室操控与野外调查，针对入侵物种介导的寄生虫稀释效应的两种具体机制——宿主间竞争与接触减少——开展检验。 实验室实验中，将单只三带伊蚊（Aedes triseriatus）幼虫暴露于8种实验组合之一，组合变量包括：是否感染巴雷特孢簇虫（Ascogregarina barretti）、寄生虫暴露期间是否共存1只白纹伊蚊（Aedes albopictus）幼虫，以及感染性寄生虫清除后是否共存1只白纹伊蚊幼虫。幼虫感染强度（预期会因接触减少介导的稀释效应而降低）并未受白纹伊蚊的显著影响。成虫感染率与感染强度（预期会因宿主间竞争介导的稀释效应而降低）在有白纹伊蚊共存时反而显著升高，表明种间竞争会增强寄生虫感染成功性，该效应可能由竞争延长三带伊蚊的发育时长所介导。 野外调查中，我们检验了潜在稀释宿主的丰度对三带伊蚊幼虫体内巴雷特孢簇虫的感染率与感染丰度的影响。分段路径分析（Piece-wise path analysis）未发现宿主间竞争影响野外寄生虫感染的证据，反而显示伊蚊属（Aedes spp.）丰度对三带伊蚊体内的寄生虫丰度存在显著直接负向影响，这与野外环境中接触减少介导的稀释效应假说一致，但该效应仅存在于树穴生境中，而非人工容器生境。 本研究结果支持“无竞争能力的入侵物种可改变本土宿主-寄生虫互作关系”的假说，但实验室与野外数据得到了不一致的结论。该差异可能源于：实验室实验检验的是稀释宿主对寄生虫感染的个体水平效应，而野外分析检验的是稀释宿主丰度对寄生虫感染的效应。 单独来看，与入侵物种的宿主间竞争会增强而非减弱寄生虫的感染成功性。与之相反，本研究的路径分析结果支持“野外环境中寄生虫稀释效应源于无竞争能力宿主的丰度升高”这一假说。