Category Archives: Insects

ODD POLLINATORS

Insects and plants are intimately linked in terms of their ecology and evolution. Insects and vascular plants both first appear in the fossil record around 400 MY ago, at the beginning of the Devonian, as terrestrial ecology changed to allow the colonization of the land.

Then about 20 MY later, the first arboreal plants appear, and insects developed wings (probably from ancestral gills – the same genes are now involved in the development of arthropod gills and insect wings). However, things really went crazy in the middle of the Carboniferous, when seed plants first appeared, and the insects underwent a massive diversification, or “radiation” as paleontologists call it.

In this period, all of the major insect groups appeared, with only one (the Palaeodictyopterida – they looked a bit like dragonflies) disappearing between then and now. Insects even breezed through the end-Permian mass extinctions around 248 MY ago, when around 95% of marine species disappeared, profiting from the changed ecosystem to undergo a further wave of radiation.

By the time the flowering plants (“angiosperms”) appeared around 100 MY ago (flowers are a relatively recent invention), the insects were established as one of the dominant features of the terrestrial ecosystem, and quickly took advantage of the new plant arrivals. Although insects (and their larvae) munch through plants, the relation can also be mutually beneficial, especially with regard to pollination. Flowering plants generally provide a sucrose reward (nectar) for insect visitors, which in turn inadvertently carry off pollen to other plants of the same species, spreading the genes about. This mutually beneficial relation is shown by the parallel radiation of angiosperms and lepidopterans (butterflies and moths).

Darwin famously predicted that the comet orchid, which has an amazingly long “nectar spur” (the structure holding the nectar – it can be over 30cm long), must be pollinated by an insect with an equally long proboscis. He was right – it turned out to be the nocturnal hawk moth, with a 35cm long proboscis.

But what happened before there were flowers? Did insects simply eat the gymnosperms and ginkos that covered the Earth, or were they still involved in pollination – and how? Were all plants simply wind-pollinated?

Two recent discoveries give some insight into this. First, back in November, a stunning set of fossils was described in Science, showing in exquisite detail the mouthparts of some Mecopterans – scorpion flies. Nowadays they are a pretty insignificant bunch of around 600 species (and, of course, they are not flies…).


The fossils (and contemporaneous amber specimens) showed long, flexible probosces, and sucky ends that the insects could have used to suck up nectar-like substances produced by gynmosperms. The authors, led by Dong Ren of Capital Normal University, Beijing, conclude:

The presence of scorpionfly taxa suggests that siphonate proboscides fed on gymnosperm pollination drops and likely engaged in pollination mutualisms with gymnosperms during the mid-Mesozoic, long before the similar and independent coevolution of nectar-feeding flies, moths, and beetles on angiosperms.

Now another insight into unusual pollinators has come from Reunion Island, down in the south Indian Ocean, next to Mauritius (despite its distance from Europe, Reunion is part of France). Writing in the Annals of Botany, Claire Micheneau describes how she set out to find out how an unusual orchid, Angraecum cadetii (related to Darwin’s star orchid), was pollinated. [See also this BBC page.] They discovered that the animal responsible was an unusual – and unnamed – cricket with unusually long antennae:

These crickets, which are nocturnal foragers, reached flowers by climbing up leaves of the orchid or jumping across from neighbouring plants and probed the most ‘fresh-looking’ flowers on each plant.

They even provide a video, which should be visible below (although perhaps not to readers outside the UK; try here if not):

This is the first time that a cricket has been described as a pollinator, but it gives some indication of the variety of ways that pollination could have taken place even before flowers.  Orthopterans (crickets and grasshoppers) appeared at the same time as the gymnosperms; although people generally assumed the insects would have eaten the plants, the example of the scorpion flies suggests they might also have played a role in pollination.

Leave a comment

Filed under Ecology (scientific), Fossils, Insects

A FLYING ADVERT

The recent Frankfurt Book Fair saw this rather unusual living advert – little flyers attached to flies. They were released into the Book Fair to delight (or irritate) the worthies of the book world who were there to wheel and deal. What are the ethics of this? Where should it stop? Here, or with the release of a skunk?

1 Comment

Filed under Insects, Videos

A silly fruit fly song

In 1907-8, Thomas Hunt Morgan began to study Drosophila melanogaster in the laboratory. Morgan wasn’t the first to focus on the tiny fruitfly – in 1901 William E. Castle had begun breeding flies in Harvard.

Mendel’s laws had been rediscovered in 1903, but Morgan wasn’t interested in inheritance – indeed he was unconvinced about what was to be called “genetics”. Morgan wanted to look at evolution, by changing the flies’ environment and inducing what the scientist de Vries called “mutating periods”.

Throughout 1907 and 1908, hapless insects were therefore alternatively whizzed round in centrifuges, frozen, boiled, made to eat horrible food, and so on, in the vain hope that important mutational changes would arise. They never did. After three years, Morgan was ready to give the whole thing up as a bad job. Although Frank Lutz had found a wing mutant in 1908, nothing like a “mutating period” had been seen.

Then, in 1910, a series of mutations affecting different parts of the flies’ bodies began to appear – trident, olive, beaded and finally white. Using these and other mutants, in the next few years, Morgan and his students laid the foundations of modern genetics.

The flies finally had their say, however, in this YouTube song. One minor criticism, however – the song says flies don’t sleep. Oh yes, they do!

Thanks to Robert Myler for spotting this video.

Leave a comment

Filed under Insects, Videos

BIG INSECTS

November 2007

One of the main theories that explains the existence of large arthropods in previous epochs is the fact that oxygen levels were sometimes much higher, allowing organisms which depend on passive diffusion, like insects, to grow larger. (This was a key aspect of a plot in last year’s TV hit Primeval which featured an unfeasibly large giant centipede from the deep past.) This is a difficult hypothesis to test, but these authors of an open access article in PNAS have done their best, looking at the evolution of trachaea in beetles.

Leave a comment

Filed under Evolution, Insects

ROBOT ROACHES

November 2007

Those Final Years who have done the Animal Behaviour course may remember me showing videos of robots behaving like ants. The same Belgian group led by Deneubourg has now turned its attention to cockroaches, as shown by their article in this week’s issue of Science. If you cover a robot with cockroach pheromone, the real roaches follow it. I’m not sure what this is really telling us, apart from indicating the power of the pheromones, or the effect of introducing another object into the cockroaches’ shelter, but the results are impressive.

BBC article (with video); Science news article, Science research article, with supplementary videos (subscription needed).

Leave a comment

Filed under Behaviour, Insects

BIOMIMICRY

November 2007

Can we use animals as inspiration for new technology? Here are some thought-provoking examples.

Guardian pictures of butterflies, geckos and the like, and their potential applications. BBC Radio 4 programme about  the Bombardier beetle and why materials science folk are studying it (click on “listen again”).

Leave a comment

Filed under Audio files, Insects

WHY ARE THERE NO MARINE INSECTS?

October 2007

There are no insects that spend their whole life cycle under the surface of the sea, and very few that spend even part of their life on or in the sea. Why not? This student-built website takes you through the various hypotheses (salinity, competitive exclusion etc) and provides you with lots of thought-provoking ideas. NB You can’t jump to the end and get “the answer”, for two reasons – a) there isn’t one and b) you have to collect the letters of a password by going through each hypothesis!

Leave a comment

Filed under Insects, Oceans