1. Vogel's (1920) assertion that the labral canal is closed ventrally by apposition of the edges of the labral groove is fully confirmed. The hypopharynx plays no part in the ventral closure of the food canal except at its base. The somewhat popular term “labrum-epipharynx” is dispensed with in favour of “labrum”.
2. The mandibular teeth vary in number round about 40. The mandibular suspension is fully described.
3. Evidence from musculature is put forward for the existence of a small maxillary palpifer not present in other Diptera.
4. Snodgrass (1935) criticizes Crampton's (1925) homologizing of the labella with labial palps because “the lobes of the fly labium have usually each only one muscle inserted directly upon it”, whereas palpi usually have antagonistic muscles. Vogel for Culex and this paper for Anopheles maculipennis show that the labial lobes of these insects have antagonistic muscles like typical palpi.
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