Meloe is a genus of blister beetles commonly referred to as oil beetles.[1] The name derives from their defensive strategy: when threatened they release oily droplets of hemolymph from their joints (legs, neck, and antennae). This fluid is bright orange and contains cantharidin, a poisonous chemical compound. Wiping the chemical on skin can cause blistering and painful swelling of the skin. This defensive strategy is not exclusive to this genus; all meloids possess and exude cantharidin upon threat.
Morphology
Oil beetle adult dorsal view
Members of this genus typically have shortened elytra and lack functional wings. They are often iridescent blue, green, or black with pits/punctures on the elytra and thorax, and a bloated abdomen. Some species of males have kinks in their antennae, which are shaped differently for different species.
Biology
As with all other members of Meloidae, the larval cycle is hypermetamorphic; the larva goes through several body types, the first of which is typically a mobile triungulin that finds and attaches to a host in order to gain access to the host's offspring. They usually climb onto a flower head, and await a bee there. They will then attach themselves to the bee. If it is a male, they wait for mating with a female. They will switch to the female when this takes place. If the bee is a female, however, she will take them back to her nest unwittingly. Once in the nest, the larvae morphs into a grub-like "couch potato" and feeds upon all of the provisions and the larva. Next, they form a pupa and emerge in various seasons depending on the species. Each species of Meloe may attack only a single species or genus of bees. Some are generalists. Though sometimes considered parasitoids, it appears that in general, the Meloe larva consumes the bee larva along with its provisions, and can often survive on the provisions alone; thus they do not truly qualify for this designation (seeParasitoidfor definition).
Upon surfacing from their underground lives as larvae, the adults feed on plants in the Ranunculaceae, Ipomoaceae, and Solanaceae families.
Mating begins when a male mounts a female and releases chemical components through the kinks on the antennae, massaging her antennae and pulling them back. This serves to calm the female. Mating then occurs, with the male transferring his cantharidin to the female during this period and she coats her eggs with it. [2]
Species
The following species are recognised in the genus Meloe:[3][4]
^Pinto, J.D., Selander, R.B. The bionmics of blister beetles in the genus Meloe and a classification of the New World species. Illinois Biological Monographs. 1970.
