Genitalia analyze is one of very important step of studying taxonomy of insects in general and beetles particularly. Not only because they are very variable in mature form but also they are very similar among individuals that not belong same species. For some group of beetles, genitalia is not the key characteristic for separate species but in some group, the male genitalia is only way to identify them to species level.
Each taxonomist developed himself a way to study his group, this posting I am going to express how I access the male genitalia of a horned rutelinae for studying without cut them off from the specimen.
Prepare a hot water cup/box for the dried specimen that collected from the field.
From left to right (below): box of hot water (now maybe warm water) with beetle specimen, soft tissue paper (toilet paper, don't apply an used toilet paper in this case, we need a clean one), foam board; above: forceps and insect pins.
Make the beetle dried by soft tissue paper, both side of the specimen.
Transfer to the foam board for fix the poission
Fixed specimen with entomological pins then you can access the last abdomen segment without moving
Prepare 2 forceps with point tips, each hand with each one.
Use the point forceps open the last segment
Then you can see the apex of the penis
Then try to pull out the penis from the abdomen
Do it slowly without damage the penis apex (it very sensitive and easy to be broken)
Release specimen by removing the insect pins
Open the mandible make them separate in a good view poisition
Turn the specimen to express position
Fix the specimen in dorsal position with insect pins again.
Under microscopic field, check the shape and position of the genitalia in dorsal view. Shape of the genitalia shows that it look like Kibakoganea dohertyi
Dried fixed specimen in a box with silica-gel in side
As your specimen full dried up, it will ready for pinning or gluing on the card board, do not forget the data label of the specimen.