Beware the wings of Summer!

Christmas is coming

Bruxas in the flat
please put the aircon on
and squash the mossies flat

Summer is coming to the Mata Atlantica, which means hot days and nights, and rain - perfect conditions for insects. This, not Halloween, is the time for witches, "bruxas", huge (up to 16cm) moths the size of bats who invade your house at night. As I mentioned in a previous blog, bruxas, (Ascalapha odorata) are of course completely harmless, if occasionally annoying, and they feed on rotten fruit. They'll probably be around until January.

Bruxas might be harmless, but other summer visitors not so much. Termites ("cupims") swarm at this time of year, males and females abandoning their nests and flying out into the sky. They are weak fliers, and blown hither and thither by the wind. When they land they shed their wings and, if they are lucky, start to make a nest from the wet trees and timber they have landed on, so if you see discarded insect wings on your furniature, watch out! Mated queens produce huge quantities of workers that build the nest where they will all live, either underground, in mounds in the pampas or fields, or as nests on the side of trees and fence posts.


As many house holders have found to their cost, termites are very good at digesting wood, which is beyond most creatures. Although some can actually do this by themselves, most have colonies of microbes in their gut who do the work for them. Humans though are having their revenge. Firstly, termites are edible and easily caught when swarming. Apparently they are best lightly grilled on a hot plate, their natural oils supplying the cooking fat. Secondly, they are potentially a source of fuel - producing hydrogen from waste wood, although nobody has quite made a termite power station yet.

And worst of all are the mosquitoes, their life cycles speeded up by the heat, and with plenty of puddles to lay their eggs. Development time for Aedes aegypti, from egg to adult, goes from 33 days at 16C to 9 days at 32, although if it's any consolation they do die younger. With more mosquitoes comes more disease, the incidence of Dengue fever for example starts to rise steeply in December before peaking in March to May.

So beware, the time of the insects is coming!

Fever in the forest - addendum

Lots of good questions! Thanks guys, it´s really nice to get feedback.

Steve, from what I know, Aedes aegypti can feed during the day, but they are more active around dusk. It´s complicated though, as Vitoria is being invaded by another species that can transmit Dengue, Aedes albopictus, and this is around all day. Worse still, it´s very nervous and flits away before finishing a good meal, so it has to bite lots of people.

I'm not sure that socks give you such immunity! Mosquitoes hunt you down by first following a trail of CO2, which is why some buzz around your face, and then smelling your sweat, which means exposed skin. Now, feet can be quite a potent source of er, odours, and the skin on the side is quite thin, hairless and easy to penetrate, so they make a good target, but not the only one. To diverge slightly, there was a famous experiment showing Limburger cheese as a good mosquito attractant, as the smell is similar to unwashed feet!

Bec, I know it sounds bizarre, but it might actually work! It is female mosquitoes that do the biting, and it´s only males that are released, after being sterilised. They mate with the females and produce infertile eggs (so you do get bitten now, just less in the future). This technique has been used to control insect pests like the Screw worm fly, or Mexican fruit flies, and in theory you don´t need any pesticides, but the problems are....
a) there is a high start up cost, you have to release lots of mossies, and sterilising them by radiation is fairly sophisticated
b) unless you live on an island, there will always be an influx of mosquitoes from outside. You just have to keep releasing indefinitely.
Still, it´s possible.

Mynah, I don´t know! They found antibodies, and virus gene sequence, but whether the bats, rodents etc would be a reservoir of infections for humans isn´t clear. In fact, what might be happening is that Dengue is evolving into Bat Dengue, Mouse Dengue etc, which wouldn´t be a problem (well, not for us).

Thanks again for the feedback!

Fever in the Forest

Now and again through the evening calm comes the sound of a powerful petrol motor, and soon afterwards the streets are filled with a thick grey cloud. This is insecticide, and they are fumigating against the mosquito Aedes aegypti. Aedes is one of the banes of mankind, in many ways, but the worry here is Dengue fever.

Dengue is a virus, and causes fever, joint pains and, even sometimes hemorrhage and death. It is incredibly common in tropical regions around the world, with about 50 million cases a year. You can´t catch it by shaking hands, or sneezing or eating the wrong foods, it has to be transmitted blood to blood, which in practice means the bite of a female mosquito of the Aedes genus. Hence the attempt to eradicate this little pest.

But does this really have anything to do with the Mata Atlantica? It´s not just the mosquito bite that causes a disease, there has to have been someone infectious to infect the insect. Or something infectious. Some animals act as reservoirs for human diseases, the sylvan equivalent of typhoid Mary. Yellow fever, for example, is notorious for infecting primate populations, so lumberjacks clearing forest are often particularly at risk.

In the Americas at least, that was thought not to be the case with Dengue, not least because it is not native here. It was brought over with slaves from Africa and immigrants from Asia, and so is not adapted for local wildlife. However, recent research in French Guyana, the French colony north of Brazil, found viral RNA in quite a few animals, including rodents, marsupials and bats. Several of these, such as the mouse opossum Marmosa murina are found in the Mata Atlantica and the presence of virus in their systems suggests that it is adapting. This is bad news for attempts to eradicate the disease.