The hypothesis of a close relationship between the suborders Holothyrida and Ixodida is re-examined based on new morphological and molecular data. Description of the larva of a new species of Neothyridae (Holothyrida), the first formal description of this instar for the suborder, does not provide additional morphological data supporting the relationship. However, because the larva is holotrichous, it does allow the first direct comparison of setation patterns among immatures of all four parasitiform suborders (Holothyrida, Ixodida, Opiliocarida and Mesostigmata). Analysis of sequence data for three loci (18S rRNA, 28S rRNA, and Elongation Factor 1-alpha), with representation of all families of Holothyrida, provided strong evidence for (1) the monophyly of Holothyrida, (2) a close relationship between Holothyrida and Ixodida, and (3) a grouping of the large bodied Parasitiformes (Opilioacarida, Holothyrida, and Ixodida), with the exclusion of Mesostigmata.