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The larval head of Protanyderus was exam- ined and documented using innovative techniques, with emphasis on internal structures. A chart listing all head muscles of dipteran larvae and other holometabolan groups is presented in the Supporting Information. The results are compared to conditions found in other nematoceran line- ages. The larval head of Protanyderus is characterized mainly by plesiomorphic character states such as the com- plete and largely exposed head capsule, the long coronal suture, V-shaped frontal sutures, lateral antennal insertion areas, a transverse labrum, a nearly horizontal plane of mandibular movements, mandibles lacking a movable dis- tal part, a mesal hook and mesal or distal combs, separated maxillary endite lobes, a comparatively complete array of muscles, and a brain only partly located within the head capsule. An anteriorly toothed hypostomal plate and dense labral brushes of microtrichiae are also likely groundplan features of Diptera. The pharyngeal filter is a possible apo- morphy of Diptera excl. Deuterophlebiidae (or Deutero- phlebiidae 1 Nymphomyiidae). The messors have also likely evolved early in the dipteran crown group but are absent in the groundplan. The phylogenetic interpretation of externolateral plates with growth lines is ambiguous. Autapomorphies of Tanyderidae are differences between the third and fourth instar larvae, the roof-like extension above the antennal insertion area, the dorsal endocarina, and the posterodorsal internal ridge. The phylogenetic posi- tion of Tanyderidae is controversial, but features of the larval head do not support a proposed sistergroup relation- ship between Tanyderidae and Psychodidae. Both groups differ in many features of the larval head, and we did not identify a single potential synapomorphy. Larval charac- ters alone are insufficient for a reliable phylogenetic recon- struction, though they vary greatly and apparently contain phylogenetic information. The evaluation of these features in the context of robust molecular phylogenies will be a sound basis for the reconstruction of complex evolutionary scenarios for the megadiverse Diptera. J. Morphol.

Relationships among families of the lower Diptera (formerly suborder 'Nematocera') have been exceptionally difficult to resolve. Multiple hypotheses based on morphology have been proposed to identify the earliest lineages of flies and place the phylogenetic origin of the higher flies (Brachycera), but convincing support is limited. Here we resolve relationships among the major groups of lower Diptera using sequence data from four nuclear markers, including both ribosomal (28S rDNA) and protein-coding (CAD, TPI and PGD) genes. Our results support both novel and traditional arrangements. Most unexpectedly, the small, highly-specialized family Deuterophlebiidae appears to be sister to all remaining Diptera. Other results include the resolution of the traditional infra-orders Culicomorpha (including a novel superfamily Simulioidea ¼ Thaumaleidae þ Simuliidae), Tipulomorpha (Tipulidae sensu lato þ Trichoceridae) and Bibionomorpha sensu lato. We find support for a limited Psychodomorpha (Blephariceridae, Tanyderidae and Psycho- didae) and Ptychopteromorpha (Ptychopteridae), whereas the placement of several enigmatic families (Nymphomyiidae, Axymyiidae and Perissommatidae) remains ambiguous. According to genetic data, the infra-order Bibionomorpha is sister to the Brachycera. Much of the phylogenetic signal for major lineages was found in the 28S rDNA gene, whereas protein-coding genes performed variably at different levels. In addition to elucidating relationships, we also estimate the age of major lower dipteran clades, based on molecular divergence time estimates using relaxed-clock Bayesian methods and fossil calibration points.

The cuticular morphology of a hitherto unknown larva from New Zealand belonging to the genus Mischoderus is described in detail. From this it appears that this larva (and probably tanyderid larvae in general) represents a much more remarkable type than can be seen from the available descriptions, the head capsule showing some morphological features unique among nematocerous larvae. Furthermore, it is established that tanyderid larvae do not represent such a primitive stage as is often claimed. However, no closer affinities to other nematocerous families can be stated in a convincing way.