Immature Stages of Phoridae
Clausen (1940) gave a cursory description of the immature stages of the Phoridae so that the parasitic and predaceous forms might be distinguished from other Diptera that may attack the same hosts.
The eggs of very few species were known by 1940, all being of simple form and several times longer than wide, the anterior end wider than the posterior and both smoothly rounded, with the chorion white and smooth.
The first‑instar larva lacks the anterior spiracles. The mature larva of Hypocera incrassata is rather elongated in form and, like many other parasite species, differs from those that develop as scavengers in the absence or great reduction of the numerous sensory spines and fleshy processes upon the cuticle of the body segments. This distinction, however, does not apply in all cases. The body segments of Hypocera are fairly distinct, though somewhat obscured by supplementary folds. The buccopharyngeal armature is of three parts, with the mandibular sclerite in the form of a single stout structure. The anterior and posterior spiracles are almost identical, are slightly elevated, and have four oval openings. The larva of S. cocciphila is more robust in form and bears a transverse row of small setae dorsally and laterally on each body segment. In Melaloncha romnai, the body segments bear a fine pubescence and a varying number of long, slender fleshy processes dorsally and laterally. The posterior spiracles are simple and circular in form. In most species of the family, these have four openings, whereas the anterior spiracles have only two. For a detailed study of the morphology of phorid larvae, the reader is referred to Keilin (19lla), who described the larvae of several scavengerous species.
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The puparia of this family are readily recognizable because of their distinctive form (Fig. 174). Instead of being circular in transverse section, the lateral margins are flattened dorsoventrally. The greatest thickness occurs in the third or fourth abdominal segments, and the preceding thoracic and abdominal segments taper sharply. The dorsum is much less convex than the ventral side of the body, and this, with the distinct lateral margins, gives the puparium a boat‑like appearance. In some species such as M. ronnai, the puparium in lateral view is somewhat S‑shaped, owing to the depression of the dorsum of the abdomen, the concavity of the anterior ventral area, and the marked convexity of the ventral surface of the abdomen. The prothoracic cornicles of the pupa project from the anterior margin of the second thoracic segment; they may be sma11, or they may equal several segments in length.
In some species, emergence from the puparium is effected by forcing off the operculum, consisting of the dorsal portion of the first and second and most of the third thoracic segments, in a single piece; in other species the operculum splits into two parts along the median line.