The embryology of Lytta viridana LeConte (Coleoptera: Meloidae). VIII. The respiratory system

The tracheal system arises as intrasegmental ectodermal invaginations in the anterolateral regions of the mesothorax, metathorax, and first eight abdominal segments. Dorsal, dorsal visceral, ventral visceral, and ventral tracheal branches from the spiracular tracheae form in most segments. A ventral visceral trachea is lacking in the mesothorax and a dorsal visceral in the metathorax. Before eclosion the metathoracic ventral visceral trachea disappears and the metathoracic spiracle becomes occluded. The longitudinal tracheal trunks develop after the segmental tracheae from cephalad branches from the spiracles. The ventrolateral trunk to the head supplies branches to all the cephalic appendages, including the antenna and labrum. The trachea to the prothoracic ganglion and leg probably represents the ventral trachea from a primitive prothoracic spiracle. The trachea to the suboesophageal ganglion and the cephalic ventrolateral trunk may represent branches from an original "labial" spiracle. An internal closing apparatus involves the spiracular tracheal wall and has a single opening muscle. The oenocyte bodies form by ectodermal cell proliferation in the posterolateral regions of the first eight abdominal segments.