#58 Christmas beetles get busy

Christmas Beetles are busy passing on their genes at this time of the year, and I am particularly pleased with the series of images I captured of one species in action.

Over two days in mid December, I found Black Nail Beetles (Repsimus manicatus) in numbers on a couple of my Callistemon shrubs. With a ladder, and a good dose of patience and a healthy sense of discovery and humour, I searched for mating pairs, and was rewarded with good views of the entire act.

Black Nail Beetles (Repsimus manicatus) are so called

because the elytra (wing covers) resemble long black

polished fingernails

Adult beetles emerge during the early to mid summer period from the soil, hence the common name of "Christmas Beetles". From Family Scarabaeidae, there are approximately 34 species of Christmas Beetles distributed throughout Australia, most commonly in the high-rainfall coastal areas of eastern states.

Life Cycle of the Christmas Beetle

The life cycle extends over one or two years, depending on species. Eggs are laid into soil or compost in the spring and early summer. Females are capable of laying between 20 and 40 eggs each. Newly hatched larvae feed on organic matter in the soil, and older larvae feed on organic matter and/or roots. Ref: Dept Primary Industries, Queensland.

The larvae have a distinctive 'C' shape and are often called curl grubs. In late winter/early spring fully-grown larvae move close to the surface and hollow out a chamber in which they pupate. Pupation lasts several weeks.

After pupation the new adults must wait in the soil for suitable conditions, usually when the soil is softened by rain, allowing them to dig their way to the surface. In very dry conditions the beetles cannot burrow to the surface, and die in the soil. In flooded conditions they will drown. Ref: Dept Primary Industries, Qld.

The underside of a Black Nail Christmas Beetle as it eats

After emerging, beetles fly a short distance to food plants to feed and mate. The females then return to the soil and lay eggs, although some lay eggs before feeding. Feeding and egg-laying may continue for several days. Adults may live for some weeks. Ref: Dept Primary Industries, Qld.

Adults are voracious feeders and large swarms can rapidly defoliate trees. Although the damage to my Bottlebrush shrubs is evident, it is not extreme, and a light prune will be all that is needed to tidy them up.

Black Nail Beetles ( Repsimus manicatus) copulating.

- notice the distinctive difference in size and

shape of the hind legs of male and female.

The Black Nail Beetle has immensely developed hind legs, with the male having thicker legs than the female. When I disturbed the beetles, they raised back legs in a horizontal posture, presumably to assume a more threatening size as a defense strategy.

It was interesting to note that the Black Nail Christmas Beetles were not attracted to the porch light of a night.

The large hooked back claws are not used in mating,

but for moving about the foliage

This image shows a thick white fluid oozing from

the female's reproductive canal

. . . . . and this image illustrates the shape of the male's

reproductive organ just withdrawn from the female

It might sound like a rather odd pastime, spying on the mating practices of beetles, but what fascinating up-close observations! And all in my garden! This is the first time I have noticed this species of beetle in my yard, so it was a beaut find.

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Christmas is different things to different people. I hope everyone stays safe over the festive season, and has reason to smile. I'd like to send a special "cheerio" to those who might be lonely, alone, unwell, low in spirit, or down on luck.

Seasons greetings from Gaye from the Hunter