UC Riverside

Dicrotelini Stål, 1859 are a small tribe of the assassin bug subfamily Harpactorinae Amyot and Serville, 1843 that is restricted to the Australian and Oriental regions. Little is known about their biology and ecology, and specimens are rare in collections. Despite drastic morphological differences, molecular phylogenies have recovered Dictrotelini as sister taxon to Ectinoderini Stål, 1859, the Old World resin bugs, that are also part of the Harpactorinae. The placement of Dictrotelini among the early diverging lineages of Harpactorinae is surprising, given their superficial similarity to Harpactorini Amyot and Serville, 1843 and other Higher Harpactorinae. In depth morphological documentation of Dictrotelini is critical to further evaluate the phylogenetic position of this small tribe. We here document the external morphology, male genitalia, and female external and internal genitalia of two undescribed, micropterous species of Dicrotelini from Thailand using macrophotography and scanning electron microscopy. Dicrotelini lack several characters that are putative synapomorphies of Higher Harpactorinae, corroborating the phylogenetic placement based on molecular data. We find that Phylinae diverged from their orthotyline sister group before the end of the Cretaceous, tribal-level taxa diversified throughout the Paleogene, and diversification within genera mostly occurred in the Neogene. Host plant repertoire reconstructions at the family level show that transitions from monophagy to polyphagy are more common than the reverse. We reconstructed the ancestral phyline host as Malpighiales, followed by Asterales throughout most of the deep splits. Species-level divergences in the two oak-associated clades are shallower than those in oaks, suggesting that they tracked their hosts. While only the first step towards testing hypotheses on ecological speciation of plants and insects, our study shows that Phylinae are a suitable system to further explore these questions.