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Table 1 Review of published descriptions of the labio-maxillary complex of Macrosiagonini

From: The earliest beetle with mouthparts specialized for feeding on nectar is a parasitoid of mid-Cretaceous Hymenoptera

Taxon with reviewed reference Maxilla Labium
Metoecus paradoxus (Linné), sensu Yablokov-Khnzoryan [45] One segmented galea atrophied, much shorter than palpomere II; lacinia short, 3 × shorter than palpomere II Ligula absent
Macrosiagon spinipennis (Gerstaecker) sensu Gerstaecker [49] One segmented galea as long as 4-segmented maxillary palpus; lacinia short, as long as palpomeres I and II combined Labium not figured
Macrosiagon bimaculatum (Fabricius), sensu Gerstaecker [49] One segmented galea 1.35 × longer than 4-segmented maxillary palpus; lacinia short, as long as palpomeres I and II combined Ligula as long as 2 distal labial palpomeres, bilobed at apex
Macrosiagon bimaculatum (Fabricius), sensu Yablokov-Khnzoryan [45] Two segmented galea 1.7 × longer than 3-segmented maxillary palpus, lacinia short, shorter than palpomere II Ligula as long as 2 distal labial palpomeres, bilobed at apex
Macrosiagon excavatum(Champion), sensu Manfrini de Brewer [51] One segmented galea atrophied, much shorter than palpomere II; lacinia prolonged, much longer than palpomeres I-III combined Ligula almost as long as 2 distal labial palpomeres with two prolonged lobes
Macrosiagon flavipennis (Leconte), sensu Manfrini de Brewer [50, 51] One(?) segmented galea 1.15 × longer than maxillary palpus; lacinia fused with stipes Ligula absent
Macrosiagon dimidiatum (Fabricius), sensu Hentz [28] One segmented galea 2 × longer than maxillary palpus; distinct lacinia as long as palpomeres I-IV combined Ligula present (but drawing is too small to be commented in more detail)
Macrosiagon dimidiatum (Fabricius), sensu Williams [47] Two segmented galea 1.4 × longer than maxillary palpus; fused stipes and lacinia shorter than palpomeres I-IV combined Ligula much shorter than 2 distal labial palpomeres, bilobed at apex
Macrosiagon dimidiatum (Fabricius), sensu Falin [48] Two segmented galea 2 × shorter than maxillary palpus; fused stipes and lacinia shorter than palpomeres I-IV combined Ligula much shorter than 2 distal labial palpomeres, bilobed at apex
Macrosiagon caffrum (Fåhraeus) sensu Franciscolo [39] One-segmented galea with subclavate apex, lacinia long. Palpus not figured Labium not figured
Macrosiagon sp. (from Zanzibar) sensu Franciscolo [39] One-segmented galea with clavate apex, lacinia knob-like. Palpus not figured Labium not figured
Melanosiagon serraticornis gen. et sp. nov Galea at least as long as 2 basal palpomeres Ligula with two prolonged lobes