Table 4 Selection of groundplan characters and apomorphies of Holometabola and of those holometabolan subgroups whose phylogenetic relationships were addressed in this study and whose monophyly was confirmed

Holometabola

•* Larval head orthognathous

•* Larval compound eyes simplified but present

•* Ocelli absent in larvae

•* Larval tentorium X-shaped

•* Retractile larval abdominal prolegs absent

• Larval cerci absent (possible reversal in Strepsiptera [homology uncertain])

•* Adult head orthognathous

• Meso- and metasternum invaginated

• Meso- and metacoxae closely adjacent medially

• Appearance of fully developed compound eyes including external apparatus in the pupal stage (reversal in Strepsiptera)

• External wing buds absent in larval stages (partial reversal in Strepsiptera)

Aparaglossata (Holometabola excluding Hymenoptera)

• Larval head prognathous

• Well-developed larval stemmata

• Larval tentorium H-shaped

• Paraglossae vestigial or absent, without muscles

• Ventral sclerites of segment VIII (gonocoxae and gonapophyses) indistinct (reversals within Neuropterida)

Neuropteroidea § (Neuropterida and Coleopterida)

• Adult head prognathous or slightly inclined (reversal in Neuroptera)

Megaloptera §

• Sensorium on antepenultimate larval antennomere

• Larval salivary duct strongly narrowed, without recognizable lumen

• Setiferous lateral abdominal gills present in larvae

Neuroptera + Megaloptera

• Mesothoracic prealare present (also in Amphiesmenoptera)

• Muscular connection between metafurcal arm and epimeral apophysis

• Aquatic larvae (with reversal)

Coleopterida (Coleoptera and Strepsiptera)

• Antenna with 9 flagellomeres or less

• Pronotum and propleuron partly or completely connected (also in Diptera)

• Metathorax enlarged, hind wings used as flight organs (posteromotorism)

• Membranous area between mesoscutellum and mesopostnotum present

Mecopterida (Antliophora and Amphiesmenoptera)

• Larval dorsal tentorial arm strongly reduced or absent

• Less than 3 larval antennomeres (reversal to 3 in some groups)

• Larval galea and lacinia extensively or completely fused (also missing as separate structures in Neuroptera and Strepsiptera)

• Larval Musculus craniodististipitalis present

Siphonaptera + Mecoptera §

• Muscle connecting profurcal arms (Musculus profurca-spinalis) present

• Acanthae of proventriculus close-set, prominently elongated