Approximately 90% of the dacine pest species can be identified accurately, and quickly, by microscopic examination of the adult. For these species there is no need for supporting evidence. The remaining 10% (mainly some dorsalis complex species) can be identified with this same method but require expert examination and may require additional supporting evidence such as the molecular diagnosis or host association records. Methods here are updated according to Drew and Romig (2013).
Only morphological diagnostic procedures and information for adult fruit flies are included here. Aside from molecular techniques, larval diagnosis has been excluded from this protocol. For information on preservation of larvae for morphological identification see Inspection of material, sample preparation and storage.
For routine morphological identification of adult fruit flies:
- Collect flies in dry traps.
- When clearing traps collect samples into a tissue. Put tissue in a small box with collection details on the outside. Samples in tissue can also be collected into a vial though this is less preferred particularly in the tropics as samples can sweat causing specimens to deteriorate. If collecting into vial a pencil or permanent pen label (not biro as it runs) should be put inside as writing on the outside can rub off.
- Store samples in freezer until ready for identification.
- Sort dry specimens in a petri dish under a binocular microscope.
- If keeping specimens after identification store in freezer to prevent deterioration.
- Do not store specimens in ethanol/alcohol/propylene glycol unless being kept for DNA analysis. They leach diagnostic colours and patterns necessary for morphological identification.
For suspect specimens requiring further identification:
- Store the specimen in a small vial with tissue to protect it until ready to pin or ship. Add a pencil or permanent ink label (not biro as it runs) detailing collection location, collection date, collection method, collector, tentative identification and identifier.
- As manipulating loose specimens with forceps tends to damage them, suspect specimens should ideally be pinned to keep them as intact as possible. If the specimen is a suspect exotic and needs to be shipped to a specialist ASAP they can be sent unpinned in a tube as above.
- Put specimen in relaxing chamber with thymol (to prevent mould growth) for 6-12 hours.
- Using a micropin, pin through the right hand side of scutum. Mount micropinned specimen on a pith stage on a pin.
- Add label to pin.
- Store pinned specimens in reference collection conditions i.e. 21°C and 50% relative humidity.
The following apparatus and procedures should be used to prepare the specimen for identification (adapted from QDPIF 2002):
- Stereoscopic microscope or stereo microscope with magnification range of 7X to 35X.
- Light source
- 90mm diameter petri dishes
- Forceps (Inox #4)
- Ensure the workstation is clean and clear of all flies before commencing.
- Adjust chair height and microscope, and turn on the light source (refer to specific operating procedures for the microscope in use).
- If applicable, record the lure and trap type or host material in which the specimen was found.
- Carefully place the fruit fly into a plastic petri dish. If examining more than one fly at once ensure there is a single layer of flies only, with room to move flies from one side of the dish to the other.
- While looking through the microscope check each fly individually. Manipulate them with the forceps so that diagnostic features are visible.
Key features (see Glossary) used for the morphological diagnosis of adult fruit flies include:
- Overall colour and colour patterning
- Wing morphology and infuscation
- Presence, shape and colour of thoracic vittae. A vitta is a band or stripe of colour.
- Presence or absence of various setae, and relative setal size (for Trypetinae). (Note: chaetotaxy, the practice of setal taxonomy, is not as important for Dacinae, i.e Bactrocera and Dacus)
Use the morphological diagnostic key and descriptions on the Species pages of this site and the Australian Handbook for the Identification of Fruit Flies to identify the species of fruit fly under microscopic examination. Use the Expanded Key to Northern Australian Species for identifying fruit flies from Cape York Peninsula and the Torres Strait.
If identification cannot be made using this diagnostic procedure and/or the specimen is suspected to be of quarantine concern, it should be referred to either a State or National authority (see Key contacts and facilities).
If the specimen is identified as an exotic fruit fly, the appropriate national authority should be notified as required under the Emergency Plant Pest Response Deed.