Skip to content

Diagnostic methods

Fruit Fly Identification Australia proposes that primary identification is undertaken using conventional taxonomy with the support of molecular genetic techniques for some species or immature stages. The diagnostic methods used to identify fruit flies are covered in greater detail in various sections on this website. These techniques are currently in use in Australia and form the basis of this national protocol.

Tephritid fruit fly adult specimens are primarily identified through an examination of morphological diagnostic characters. Morphological identification of third instar larvae is possible for some species but not all (White and Elson-Harris 1992).

Molecular techniques are useful for the identification of eggs and early instar larvae, damaged or immature adults or adults of cryptic species.

Molecular data, primarily generated via direct DNA sequencing of diagnostic markers, may be necessary to support inconclusive morphological identification. There are several circumstances for which this might be necessary.

Firstly, for immature life stages, only third instar larvae (and some pupae) of some species are identifiable via visual examination (e.g. White and Elson-Harris 1992).

Secondly, there are numerous examples of ‘problematic’ species pairs and groups that are closely related and/or the adults are near morphologically identical.

Thirdly, significant intraspecific variation in key morphological characters (e.g. scutum colour pattern), occurs in many widely distributed species. For all such situations, molecular data may improve species diagnosis.

It relies on good specimen preservation, either dry or in a high percentage ethanol (the closer to 100% ethanol the better) or propylene glycol. Water, moisture and humidity in samples cause DNA degradation.

Molecular protocols require a laboratory to be set up for molecular diagnostics, but can be conducted by almost any laboratory so equipped. Reference data sets built from verified specimens are provided on this website for all molecular diagnostic markers discussed here, and additional published sequence data is available online.