Tuesday, 15 October 2013

Sexing flower beetle (cetoniidae) larvae

Sexing flower beetle (cetoniidae) larvae, such as mecynorrhina ugandensis, protaetia or goliathus is not very difficult, however, requires some practice. It is much easier when larvae are reaching their third (L3 stage). In smaller larvae, such as at their L2 larval stage, finding the "right spot" is quite difficult because of their size and because of their mobility:  small larvae are normally very active:) With some practice anyone can do it. Determining the sex of the larvae by the size of its head capsule is not reliable, simply because the smaller larvae of the same age will have the smaller head capsule, irrespectively whether it's male or female.  It is best to see it in larvae which are clean of dirt and debris. On the bottom (ventral) side approximately in the middle of the last abdomenal segment in males of cetoniidae there is a small black slit/spot which is a part of  such-called "Harold's organ" (please see the photo of the L3 male larvae of the Mecynorrhina ugandensis, on the left). The spot may often look like as a hair root spot, apart there would not be any hair growing from it. The bigger larva is the bigger the size of the spot will be. That's why it is more easier to determine the sex of bigger larvae, which also normally less mobile than smaller larvae. Females (photo on right) do not have such black spot.