Pests > Pest Techniques > Techniques > Weevil genitalia preparation, identification, PNG
Pests Pest Techniques Techniques Weevil genitalia preparation, identification, PNG
Weevil genitalia preparation
| February 2003. Papua New Guinea asked about the preparation of weevil genitalia. A response from the Centre of Dry Tropics and Agriculture, Australia, suggested that the method used for mounting genitalia of Staphylinid beetles for identification purposes could be used. These beetles, collected from pitfall traps, were stored in 70% ethanol. The abdomen was dissected by opening the tergites and removing the genitalia with fine needles. The genitalia were dehydrated in absolute alcohol, and then transferred to xylene and mounted in Canada balsam on plastic micro slides.
Alternatively, follow the method used by the Beetle Diversity & Evolution Research Group, The Natural History Museum, London.
- Relax the whole insect (in alcohol, it may already be relaxed, if dry, then the insect and pin can be put into a damp atmosphere (relaxing box) or pinned over (not in!) hot water in a plastazote strip;
- Using a pin and forceps prise the abdomen away from the thorax, inserting the pin between the first visible sternite and the metasternum as a lever.
- Remove the abdomen and place in hot 10% potassium hydroxide until muscles are mostly dissolved.
- Place into distilled water and, under a dissecting microscope, carefully cut or tear the terga from the stera along one side of the abdomen.
- Cautiously remove macerated muscle tissue. Care must be taken with females not to accidentally remove the spermatheca at this phase.
- Once the macerated tissue is removed, place in fresh distilled water and remove the last tergite (pygidium if male), together with the genitalia. If the insect is male, the last sternites (the hemisternites at the genital opening), will come away simply with the tergite.
- The genitalia, spiculum relictum / spiculum gastrale, and the apical tergite and hemisternites (male) can now be examined. The genitalia should be carefully dissected away from the genital chamber to be seen clearly. The vulva and bursa of the female will often expand in the water, but collapse within around 15 minutes; if possible the shape should be captured in the expanded phase, since there are often characters to be seen.
- The genitalia can be preserved in glycerol in a vial pinned with the insect. Microscope slide preparations can obscure the 3-dimensional structure.