Thrips In Fossil Evidence

Amber is a hard resinous material made from tree sap. I have discussed its formation in a previous post. In 2009, amber deposited around 100 million years ago was found in the North Coast “Basque” area of Spain. The amber has numerous “bioinclusions” including tiny insects that are preserved in fine detail. Study of these fossils provides clues about life on earth 100 million years ago and helps to reconstruct the history of life on earth.

Pollination of plants by insects is an important feature of our ecosystem. The earliest plants were not insect pollinated. There is interest in reconstructing how pollination first evolved. A recent report in PNAS describes thrips with grains of pollen attached to hairs on the wings and body reminiscent of the hairs on extant pollinator species. These Thrips are the earliest known pollinators. Thrips as ancient pollinators is interesting because pollination is not associated with modern thrips.

Pollen grains are unique to the plant species that produces them and can be used to identify the plant. In this case, the pollen on the thrips is similar to pollen found on Ginkgo trees. Why did the thrips develop hairs for transporting pollen? The authors speculate that the thrips transported pollen from male Ginkgo trees to provide additional nutrients for their larvae in flowers of the female Gingkos. Pollen is much higher in protein than other plant tissue and would promote development of the larvae. Ginkgos have male trees with pollen and female trees with flowers but no pollen. The absence of pollen makes Ginkgo flowers less nutritious than flowers of other plants. Pollen transport by adults to feed their larvae would be a useful adaptation for feeding on Ginkgo. Even though the Ginkgo suffers some damage by feeding thrips, the pollination services may have been a net benefit to the plant.

Studies of modern pollinators reveal that both the plants and the insects benefit from their interactions. The plants gain by increasing the probability that their pollen will find a flower and produce more offspring. The insects gain more nutrition that increases the number of their offspring. Pollination is a winner for both insects and plants.

Pollen grains from 100 million years ago attached to fossil thrips.
Image: Penalver et al.
www.pnas.org/cgi/doi/10.1073/pnas.1120499109

Tulip Tree Scale

The State Tree of Indiana is the Tulip Tree. Although it feeds on tulip trees, the Tulip Tree Scale is NOT the state insect. Scale insects have sucking mouthparts that drill into tissue for feeding. The Tulip Tree Scale taps into the phloem of the plant. Plant phloem is very high in sugar and low in other nutrients. Insects that feed on phloem typically secrete large amounts of sugar and water as waste in order to get enough of the other nutrients. The sticky droplets provide food for bees, wasps, ants, beetles and many other insects. The droplets can also make a sticky mess on a car windshield, much to the irritation of motorists.

Tulip Tree Scale
Photo: University of Delaware

This year, high populations of Tulip Tree Scale are damaging trees in Indiana. We suspect that the higher population is in part due to a mild winter in 2012. Cold and freezing can be a major mortality factor for overwintering insects. There are a number of insect natural enemies that can keep the scale population under control. Some of the weakest trees will be killed by the scale insects. Hopefully, the natural enemies will supply enough control of the scales to prevent widespread damage to our Tulip Trees.

Red Admiral Migration

The Red Admiral Butterflies have been out in large flocks this spring, not only here in Tippecanoe County, Indiana but across the northeastern US and into Canada. In the fall, the Red Admiral Butterflies migrate south for their winter generation. They lay eggs and develop on plants in the South. In the Spring, their descendants begin the trek north.

Atypically large migrations have been periodically reported over the last 100 years in both North America and Europe. A mild winter throughout much of the Eastern US has been followed by flocks of Red Admirals in very large numbers. The reason for large migrations is not known, but mild winter temperatures are a suspected factor. Accurate counts of the populations are difficult, but much anecdotal information suggests that the current migration may be much larger than the large migration reported in 1990. Some observers are suggesting that this may be the largest recorded migration of Red Admirals.

Here in Indiana, the population of Red Admiral adults is noticeably smaller than it was 2 weeks ago, but a substantial, and larger than typical population remains here. To our north the warm weather in Southern Canada is leading to sightings of Red Admiral at much earlier dates than is typical.

Red Admiral Butterfly

Malaria Fighting Fashion

Clothing treated with insect repellent or insecticide has been available for a number of years. In the US, mosquito repellent clothing is popular with hunters and primarily available in styles that are popular with outdoorsmen. There is no reason why the insect repellent properties could not be added to other fashion styles.

The Njehringe Collection
Photo: Digital Trends

Two fashion design students at Cornell University who were born in Africa, recently put together a collection that brings insect repellent fabric to the world of high fashion. Their collection was inspired by the continuing epidemic of malaria in Africa. The collection, called “Njehringe”, features fabrics that are hand dyed in Gambia. The goal is to create a line of clothing that is fashionable, appealing to people who live in malaria infested areas and hopefully will contribute to the fight against malaria.

Friday Cat-erpillar Blogging: Butterflies as Botanists

In 1884, Fritz Muller wrote a letter to the Journal Nature with the title, “Butterflies as Botanists.” The letter concerned the classification of a plant genus, Brunfelsia which for many years had been assigned to the snapdragon family. Muller noted that botanists had reclassified Brunfelsia, moving it from the snapdragon family to the potato family (Solanaceae).

Fritz Muller was interested in a group of related butterflies in the Tribe Ithomiini. This group all fed on plants in the potato family with the exception of a single genus of caterpillars, the (Thyridia) that fed on Brunfelsia. Moving Brunfelsia from the snapdragon family to the potato family meant that all of the caterpillars of the group fed on plants in the potato family. Muller remarked, “Thus it appears that butterflies had recognised the true affinity of Brunfelsia long before botanists did so” (i.e. it belongs in the potato family).

The specialization of related caterpillars on closely related plant species is a pattern that is frequently repeated. In the 1960s, ecologists proposed a model for how this pattern arises.

The model for the process is as follows.
1. A plant species evolves a defense (often chemical) that protects it from herbivores.
2. The defense allows the plant species to expand its range and successfully compete with other plants in its new range.
3. The plant species in its new range evolves adaptations to local environmental conditions and eventually radiates (over many generations) new species.

The chemical defenses of the ancestral plant species are retained in its descendants. This explains the patter of closely related plants containing similar toxins (chemotaxonomy) that is used by Botanists to aid the classification of plants.

Insects are excluded from feeding on plants in this group until one or more insect species evolves an adaptation that breaks through the plant defense. The caterpillar part of the process proceeds as follows:
4. An herbivore species develops a mechanism to break the plant defense.
5. The herbivore species expands its range to include many of the species in the plant group.
6. The herbivores in the new range evolve adaptations to local environmental conditions and eventually radiate as new species.

In this manner the pattern we observe (closely related species of caterpillar feeding on closely related species of plants) is produced. Caterpillars, it turns out, are good botanists because they are good chemotaxonomists.

Black Swallowtail Caterpillar Feeding on Parsley
Black Swallowtail and its close relatives feed on plants in the carrot family.

Inadvertent Entomophagy

In North America, insects are rare in the diets of Canadians and US residents, In most of the rest of the world, insects are a common part of the diet. Not everyone will eat insects intentionally, but 100 percent eat insects inadvertently. Despite our best efforts at sanitation, many insects are so small and inconspicuous that removing them from all the food is impractical. Fruit flies can deposit eggs on a tomato and eggs hatch into tiny larvae before the tomato can be harvested and sliced onto a sandwich. Many tiny insects are found in spices and fresh produce. Most people don’t know and don’t consider the fact that they are consuming tiny insects with most meals. Most insects are harmless when eaten and pose little threat so why should it be an issue?

Caterpillars may indavertently consume mites and small insects along with the leaves they eat.

Humans and other vertebrates are not the only inadvertent consumers of insects and other terrestrial arthropods. Shirotsuka and Yano recently observed that caterpillars feeding on leaves infested with spider mites consumed many of the mites along with the leaf. The mites were not deterrent to feeding and caterpillars showed no preference for uninfested leaves over those with mite populations. Consumption of mites is not an issue for caterpillars. Insects too can be Inadvertently Entomophagous.

Living With Invasive Termites

Entomologists in Florida are once again battling the tree termite, Nasutitermes corniger. The tree termite is a native of the Caribbean that first appeared in Florida in 2001. Eradication was accomplished in 2003, but the problem has reemerged. Is it a failure to eradicate a decade ago? Or is this a new introduction? This is one of the questions to be answered. The termite was thought to have arrived in solid wood packing material (wood shipping pallets) in 2001.

Although headlines describe it as a “Dangerous” termite, the primary danger is damage to landscapes and buildings. Unlike the more familiar subterranean termites, the tree termites build nests above ground with the queen in the center of the nest. They occasionally make nests on the sides of houses. The termites will feed on living trees as well as dead wood. Like other Nasutitermes species, Nasutitermes corniger lacks the large mandibles present in most termite species. Nasutitermes species have soldiers with “nozzle heads” that can spray enemies with toxic chemicals, including pinene and limonene.

Eradication attempts are again underway. The current infestation has all been located within about a mile of the site of the original infestation. Nasutitermes corniger colonies produce winged reproductives in the spring that can disperse and establish new colonies at large distances from the nest. The Florida Department of Agriculture hopes to eradicate the infestation before it spreads. Eradication may be possible while the population is small. If it spreads, residents will be affected by these termite invaders for years to come.

Money quote from an affected homeowner (Sun-Sentinel):

They got into the tool shed and ate our stack of firewood. We went to pick it up and there was no wood left.

Hopefully, the homeowners were not taking their firewood on camping trips and potentially moving the termites to new locations.

Left: Tree Termite Nest
Right Tree Termites, Nasutitermes corniger