This video details the steps needed for Trogoderma adult beetle dissection. It has been produced by the Department of Agriculture and Food, Western Australia, with CRCPlant Biosecurity.
Methods and dissections have been done by Andras Szito, Script by Andras Szito and Cameron Brumley, Production, editing and narration by Cameron Brumley, and photography by Pia Scanlon.
Khapra beetle, Trogoderma granarium, is recognised as one of the world's most destructive pests of grain products and is subject to strict quarantine measures in many countries.
Their reliable identification and separation from dozens of very similar looking Dermestidae species is crucial to maintaining a country's area freedom.
Adult specimens are to easier to identify than larval forms, though they are often found dead, and damaged from grain movement. Species level identification requires examination of the genitalia which are usually protected inside the abdomen.
It is important to have on hand the right equipment to carry out the dissection.
We recommend using quality fine pointed forceps and scissors.
The choice of scissors is very important, as it is likely that poorly suited scissors will damage the specimen.
We use scissors with 45 degree bent blades and a 2mm cutting edge.
A range of home-made micro tools can also be useful to have on hand.
For genitalia dissection the adult beetles first need to be heated in hot 10% KOH or NaOH solution.
This helps soften the body contents and begins to dissolve the internal tissues.
Here, the preserving ethanol is siphoned off and KOH added to the vial.
The specimens are then heated to around 70 degrees centigrade for 15 to 20 minutes, preferably using dry block heater where the temperature can be controlled.
The specimen is then placed back in ethanol into a cavity glass or concave microscope slide ready for dissection.
First the abdomen is separated from the body by pressing at its base.
The KOH should have softened the specimen enough for it to separate easily.
For female beetles, the tergites are then cut or ripped laterally leaving the last segment untouched.
This is where quality forceps can make a difference.
Here, we are carefully holding the abdomen with one pair and using the other pair of forceps to tear the more flexible tergites free.
These stages can be carried out under a simple stereo microscope.
In this image you can see that the KOH has not properly dissolved the abdominal cavity contents.
The abdomen should be placed back into warm KOH until the desired outcome is reached.
With this specimen we use a slightly different technique to separate the tergites.
After separating the abdomen from the body it is carefully held with one pair of forceps.
The other pair of forceps are compressed and inserted into the abdomen cavity and are then and expanded.
The abdomen should separate along the edges of the tergites.
It can then be more easily separated further if need be.
Commonly, with male specimens the genitalia can simply be pushed out with some gentle pressure.
Here you can see the male genitalia further removed from the abdomen.
After being placed on a slide, using micro tools we are carefully separating out the male aedeagus from the remaining tissue.
Care is needed during this process as it can be easily damaged.
After it has been orientated correctly a coverslip placed over the mounting medium.
Here we have used glycerol as a short term mountant.
The adeagus is now ready for examining.
From the female genitalia we have mounted in a similar fashion the sclerites in the bursa copulatrix.
These are more robust and less prone to breakage.
Once examinations have finished the separate body parts, including the genitalia, should be mounted on a cardboard rectangle for curation as shown.
Water miscible glue is recommended so the specimen can be easily soaked off if further examination is required.
Housing the genitalia in a microvial with glycerol is not recommended as it has a reduced lifespan.