Thursday, 24 December 2009

Love Bugs

"Tis the Season..." and so on. At this time the world seems in a precarious state. What with Climate Change and the economies of many countries on the brink, it is somewhat reassuring to observe that life goes on at some levels as it always has. "Love Bugs" are so-called for obvious reasons. These are unassuming little flies in the family Bibionidae. I recall them with pleasant distant memories as a boy in San Francisco when a large species emerged each spring, in March, hence the common name in North America "March Flies". This fly was a "relict" of the sand dune fauna that once existed along the coast in San Francisco. This wonderful habitat is mostly gone now and I suspect one would have to look diligently to find one of these flies today. In the 1940's before the SF sand dunes were eliminated for homes, these flies were known to most residents as they were found on windows and plants in the gardens for a brief period in spring.

We have a dominant species in the northern tropics, Plecia amplipennis Skuse. This species is found on the light sheet most nights and can be seen resting, or mating on vegetation during the day. These flies feed on pollen and nectar and are commonly seen on native and exotic flowers. Their larvae live in the soil where they are part of the "decomposing community". Judging by the numbers of adults, the larvae must be very common in the soil and, as such, are probably important in returning leaves and other biological material back into the soil for use of other members of the community.
Males like the one above have more rounded heads and may not have functional mouthparts. They may not feed at all. Females, like the one on the right in the first photo have elongate mouthparts that enable them to reach deep into flowers for nectar and pollen.

This species exhibits a mimicry pattern that is not uncommon in tropical insects--a reddish orange fore part and a dark or black remaining part of the body. Some species are highly toxic to potential predators such as lizards or birds. This fly may also be unpalatable since it is often left alone by birds that visit the light sheet for their breakfast.

The reference below indicates there is room for taxonomic work in the Bibionidae.

Hardy, D. E. 1982. The Bibionidae (Diptera) of Australia. Invertebrate Taxonomy, 30: 805-855.

Friday, 18 December 2009

Sleeping Death

Wandering around the other night with a group from the Museum of Victoria, we came across this phenomenon. This group of halictid bees are sleeping as a unit. This is not too surprising as males of many non-hive, solitary bee species spend the nights sleeping together in clusters on leaves or twigs. To facilitate this behaviour, they usually return to the same site night after night. During the day they cruise around looking for virgin females with which to mate. Some males have well defined territories but still return to the same place to sleep. Bees are not the only insects that sleep in aggregations. We know of many unrelated insects such as bugs, beetles and even some flies with similar habits.

In this case, site fidelity works against the bees. Minute fungal spores greet the bees as they return to sleep and thus they become infected. The amount of time it takes for the infection to grow and kill the bee is unknown but the infected bee may fly around while the fungus grows within his body. Eventually, the bee takes his final sleep and does not awake The developing spores of the fungus can be seen as they await to “dust” newcomers to the night roost.

Like soldiers in a line, this group of sleeping male halictid bees seems normal enough. But most are doomed.

This group on an adjacent leaf never awoke one morning. They have been killed by a parasitic fungus. Two of the bees on the right are readying themselves to assume their "death pose" as the fungus can be seen on their antennae.

The fungal spores are clearly seen in this individual bee. The spores can be air borne and infect others as they return to the site night after night. Or bees can be infected simply by coming into contact with the spores that are on the leaves themselves.