Scanning Microscopy


The antennae, palps, and mouth parts sheath of Megaselia halterata (Wood) (Diptera, Phoridae) were examined by scanning electron microscopy to locate putative olfactory sensilla (POS). Most POS were found on the third antenna! segment (Johnston's organ). These POS included a lanceolate peg, a bulbous peg, and two types of pit sensilla. Female flies could be distinguished from males by the predominance of the lanceolate peg on the female Johnston's organ. One type of pit sensillum with a single exterior opening was located below the cuticular surface and housed several pegs. The other type of pit sensillum was domed with a single exterior opening, housed a single peg, and the lower half of this sensillum was embedded into the wall of the Johnston's organ. This type of pit sensillum was also found on the sixth antennal segment of both sexes. A bulbous peg was found on the palps of both sexes. No POS were found on the mouth parts sheath. Specimens were prepared in the traditional manner for scanning electron microscopy examination. Also specimens were embedded in Paraplast and sections of the Johnston's organ clarified the internal structure and distribution of the pit sensilla on this organ.

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