The postembryonic history of the somatic musculature of the dragonfly thorax

From the first larval instar until the time of the final transformation into the adult the thoracic muscles are numerically the same. The muscles increase in fiber number with the growth of the larvae. There are two types of larval muscles: a. functional (striated and of considerable diameter) b. non‐functional (unstriated and of narrow diameter). The non‐functional muscles are mainly the prospective wing muscles of the adult. They grow most in diameter at the time of the final transformation. The positions of attachment of both types of muscles undergo no marked replacements during transformation, although the skeletal parts to which they are attached may become greatly modified. The larva has numerically more muscles than the adult. Extensive obliteration of the trunk leg muscles and of some neck muscles takes place. The intrinsic leg muscles of both the larva and the adult are the same. There are no anlagen of the adult muscles in the larval labium, and myoblasts probably form the adult musculature of this organ. The wing muscles of adult Anisopterid dragonflies insert close to the articulations of the wings on apodemes arising from membranes, or on discs arising as internal invaginations of detached, lateral, tergal plates. During the metamorphosis of its musculature, a dragonfly exhibits every essential phenomenon that a so‐called ‘holometabolic’ insect does.