Paired elements of the proboscis, arising posterolaterally between the labrum and the labium (ex McAlpine 1981).
In my opinion, a visible lacinia and a ventral appendage are part of the stem-species pattern of the Chloropidae family-group, because these characters are present in the Acartophthalmidae and in the stem-species pattern of the Carnidae. The maxilla lacks lacinia and ventral appendage only in the carnid Neomeoneurites (Hennig 1972), which can be interpreted as an apomorphy.
A synapomorphy for the Milichiidae and Chloropidae is the absence of the ventral appendage, which was for the first time studied by Frey (1921). In addition, the lacinia is very small or absent: in the Milichiidae it is always absent, whereas in the Chloropidae there are species in which the lacinia is very short and species in which it is completely absent.
The reduction of the lacinia occurs convergently in several schizophoran families, for example in the Asteiidae, Ephydridae, Periscelididae, Platystomatidae and Pyrgotidae. Both lacinia and ventral appendage are absent in the Camillidae and Calyptratae (Frey 1921). The presence or absence of the ventral appendage has not yet been used in phylogenetic systematics and the character is poorly known in most families. Consequently it is not known whether the ventral appendage evolved once or several times in the Schizophora. If it evolved once, then this would support the hypothesis that the loss of the ventral appendage is a synapomorphy for the Milichiidae and Chloropidae. If the ventral appendage evolved several times within the Schizophora, then it could be possible that the ventral appendage is absent in the stem-species pattern of the Chloropidae family-group and evolved convergently in the Acartophthalmidae and within the Carnidae.
The palpi are short and clavate in the stem-species pattern of the Chloropidae family-group. The plesiomorphic state of the palpi is represented in the stem-species pattern of the Milichiidae. Within the Milichiidae, in the stem-species of Aldrichiomyza+Xenophyllomyza the palpi are apomorphically long and thin and in Phyllomyza+Microsimus they are long and thick (ex Brake 2000).
Each maxilla is composed of a basal cardo and a distal stipes. The stipes bears the principal maxillary blade (endite). It has been interpreted by some authors (Crampton 1942, Snodgrass 1944) as the galea, but by others (Imms 1944, Wenk 1962, Hennig 1973) as the lacinia; the latter interpretation is adopted here. The stipes also bears a maxillary palpus, usually referred to as the palpus (ex McAlpine 1981).
sing.: maxilla