"The monophyly of the Endopterygota (= Holometabola) is considered firmly established, except that the evidence for including the Strepsiptera in this taxon is ambiguous. Recent work on the strepsipteran wing structure has led to rejection of a suite of putative Coleoptera + Strepsiptera synapomorphies. A hypothesis of a Strepsiptera + Diptera monophylum has newly been proposed on the basis of molecular data and explained in terms of homeotic mutations; some difficulties in this hypothesis are pointed out. A basal dichotomy of the Endopterygota in a Coleoptera + 'Neuropteria' assemblage and a Hymenoptera + 'Mecopteria' assemblage is a weakly supported working hypothesis. The monophyly of the Megaloptera has recently been challenged, but is tentatively upheld. Molecular data support that the Mecoptera (inclusive of Nannomecoptera) + Siphonaptera are a monophylum, but the monophyly of the former with respect to the latter requires renewed scrutiny. The diversification patterns within the large endopterygote orders are briefly compared."
Kristensen independently points out the possibility of a long branch problem causing the Strepsiptera+Diptera grouping.