I grew up in a house with a large backyard full of trees and other plants next to several small forest patches. As a result, moth were always very common visitors at night, especially during the warmer months. One that always called my attention was a moth with a beautiful pattern in its wings.
Only recently I found out that its name is Pantherodes pardalaria, properly called the leopard moth. Its wings have a yellow background marked with several metallic gray spots with a black outline and a black center. Truly beautiful! A very similar pattern is found in all species of the genus Pantherodes, being the most clear characteristic that defines it.
The leopard moth occurs from Mexico to Argentina and is very common in southern Brazil. It belongs to one of the most diverse families of moth, Geometridae, characterized by their caterpilar, called inch worm, that walks as if it were measuring the ground, hence the name Geometridae (from the type genus Geometra, “earth measurer”).
I wasn’t able to find much information on the leopard moth, though. Its caterpilars seem to feed on nettles (family Urticaceae). In Mexico, the caterpilars were historically eaten as food by the Aztecs and considered a food of high value, and the practice may still occur today among some humans groups.
And that’s all I got. Despite being beautiful and easily noticed, the leopard moth is one more poorly known species.
It’s finally time to introduce another beetle, and I decided to go on with a member of the family Chrysomelidae, one of the most diverse and important in the world. The chosen species, Aspidimorpha miliaris, is commonly known as the spotted tortoise beetle.
Native from the Indomalayan region, the spotted tortoise beetle occurs from western India to Taiwan, the Philippines and Indonesia. It measures 1.5 cm in length and, as usual among tortoise beetles, the elytra (hardened forewings) and the pronotum (the foremost dorsal plate of the thorax) are widened and cover the whole body. These structures are transparent and the elytra also have many black spots. The body seen below this transparent armor varies from white to yellow and orange.
The spotted tortoise beetle calls attention not only because of its beautiful color but also because its larvae feed voraciously on plants of the genus Ipomoea and related genera, which include, among others, the sweet potato. Due to its habitat being near the equator, the spotted tortoise beetle is able to reproduce during the whole year, although its peak in abundance seems to be around June.
The eggs hatch about 10 days after being laid by the female and the larvae pass through five instars during a period of 18 to 22 days, after which they molt into a pupa that, about a week later, turns into the adult. The larvae live in groups and have a pale body marked with four black spots on the dorsal side of most segments. There are also some spiny projections running along the margins of the body.
Due to the spotted tortoise beetle’s status as a pest in sweet potato plantations, biological forms to control it have been studied and include the use of leaf extracts as pesticides, as well as parasitoid wasps as predators of eggs. On the other hand, the beetle itself could be used as an efficient agent to control the spread of some invasive species of Ipomoea.
This is how nature acts. Your enemy on one side can be your friend on the other.
Bhuyan M, Mahanta JJ, Bhattacharyya PR (2008) Biocontrol potential of tortoise beetle (Aspidomorpha miliaris) (Coleoptera: Chrysomelidae) on Ipomoea carnea in Assam, India. Biocontrol Science and Technology 18(9): 941–947. doi: 10.1080/09583150802353705
Last week I presented a nice Australian acacia, the golden wattle, so today I decided to present a small creature lives on its branches. Called Sextius virescens, this insect is commonly known as the wattle horned treehopper, acaciia horned treehopper or simply green trehopper. It is a member of the order Hemiptera and the family Membracidae, commonly known as treehoppers, which are closely related to cicadas and leafhoppers.
The body of the wattle horned treehopper measures about 1 cm in length and is mostly green, but the legs are brown. There are also two horn-like projections on the thorax that have a brown to black color and another long extension of the thorax that lies over the abdomen. It lives in groups on the branches of acacia trees, with the individuals usually aligned on the branches.
As all treehoppers, the wattle horned treehopper feeds on the sap of the plants in which it lives, sucking it with its adapted mouth parts. They excrete a sweet liquid called honeydew that atracts ants. Such ants usually feed on the nectar produced by the acacia’s extra-floral nectaries and defend the tree against other herbivores. However, the wattle horned treehoppers make ants turn their attention to them instead of the plant. Delighted by the honeydew, the ants stop defending the tree and start defending the treehoppers, which is not at all good for the plant.
But that is nature. One creature always trying to explore the relations between other creatures to take the best to itself.
It’s time to introduce a new insect order here and, again, this is a complicated taxon. The order Trichoptera consists of small moth-like insects known as caddisflies. They are closely related to moths and butterflies, the order Lepidoptera, being a sister-group of them. Having 10 times fewer species than the order Lepidoptera, the order Trichoptera is less common and much less popular, so that it is hard to find species that are well studied to present here.
The species I picked is called Glyphotaelius pellucidus and popularly known as the mottled caddisfly or mottled sedge. It lives in middle and northern Europe and has the typical life cycle of any caddisfly.
The larva of the mottled caddisfly inhabits still and slow-running waters that are overgrown by trees, especially alders, oaks and beeches, in areas of lower altitude. As usual among caddisflies, the larva of the mottled caddisfly builds a silk case (a “caddis”) in which it lives and attaches pieces of debris, especially leaf fragments of the trees mentioned above, to make it stronger. In this species, the fragments that are attached make the case very large and characteristic. To the sides of the case, the larva attaches small and irregular leaf fragments, while to the dorsal and ventral sides, it attaches large, circular sections that are much wider than the larva’s body.
The larva lives several months, from about October to April, and feeds on leaf fragments, the same material with which it builds its case. In April, the larva turns into a pupa which, usually during summer (around June or July), turns into an adult. The adult is not aquatic as the larva and the pupa. Thus, the pupa swims to the surface before breaking and releasing the adult. During this moment, the adult is very vulnerable to predators, especially fish. This is why fake adult caddisflies are commonly employed as fishing baits.
If the adult menages to leave the water alive, it still has to spend some time waiting for its wings to dry, which is another very vulnerable moment. The color of the adult is brown and the wings have a mottled pattern of dark and light marks that makes it resemble a fragment of dried leaf.
Adult caddisflies in general rarely eat and this is not different with the mottled caddisfly. The only purpose of adults is to mate and lay eggs. After mating, the female lays the eggs in a mass on the surface of leaves hanging over a water body. One female may lay up to six egg masses, which decrease in size from the first to the last, and then dies. When the eggs hatch, the larvae fall into the water, restaring the cycle.
Crichton MI (1987) A study of egg masses of Glyphotaelius pellucidus (Retzius), (Trichoptera: Limnephilidae). In: Bournaud M., Tachet H. (eds) Proceedings of the Fifth International Symposium on Trichoptera. Series Entomologica, vol 39. Springer, Dordrecht. doi: 10.1007/978-94-009-4043-7_30
Otto C (1983) Behavioural and Physiological Adaptations to a Variable Habitat in Two Species of Case-Making Caddis Larvae Using Different Food. Oikos 41(2): 188–194. doi: 10.2307/3544262
Rowlands MLJ, Hansell MH (1987) Case design, construction and ontogeny of building in Glyphotaelius pellucidus caddisfly larvae. Journal of Zoology 211(2): 329–356. doi: 10.1111/j.1469-7998.1987.tb01538.x
Finding efficient ways to deal with agricultural pests in crops is a challenging work. Currently, as we all known, the main strategy to control such pests is the use of chemical pesticides. However, this approach only serves the interests of those seeking profit over well-being, as we all know that such pesticides increase the risk of several health issues in those consuming the crops. More than that, chemical pesticides not only kill the targeted pest but many other life forms, causing a devastating effect on ecosystems.
Fortunately, there has been an increasing interest in finding alternative, healthier ways to deal with the problem. One way is the production of genetically modified organisms (GMOs) that are naturally resistant to pests. There are, however, two main problems with this approach. The first one is that the population in general has an irrational fear of GMOs, apparently believing that they can be more harmful than the poisonous chemical pesticides, which is completely absurd. The second problem with GMOs is that the technology to create them is dominated by the same companies that produce most pesticides and, as all big companies, only seek profit and do not give a damn about the people and the environment.
A third strategy is the use of natural enemies of the pests to control them in organic farms. Although many natural enemies are great doing their job, they may also cause negative impacts by interfering with the surrounding ecosystems. Many crop pests are not native from the area where they are pests, i.e., they are invasive species and, in order to control them efficiently, a predator from its native area must be introduced as well, and this predator may end up becoming a threat to other species that it elects as food.
Fortunately, some nice strategies have been recently developed. One of them includes the use of additional plants in the fields that change the way that pests behave without posing a threat to surrounding areas. These additional plants consists of two types: trap crops and insectary plants.
A trap crop, as the name suggests, is an additional crop that is not intended to be commercially exploited, but serves as a trap for the pests. Instead of attacking the main crop (called the ‘cash crop’), the pests are attracted to the trap crop, reducing their density in the cash crop. This system is more efficient if the trap crop is similar to the cash crop, such as another plant of the same genus, or another variety of the same species, because it must be as attractive to the pest as the cash crop, or perhaps even more attractive.
Insectary plants, on the other hand, are intended to attract other insects to the plantation, especially predatory insects that prey on the agricultural pest. Insectary plants should produce flowers in abundance, thus attracting many insect species, which will increase the interest of predators in the area. However, when used alone, insectary plants will only provide predators to control the pest in crop plants that are near the insectary plants and, as they are usually planted in an area surrounding the plantation, they would not protect the plants that are near the center of the plantation.
In a recent study, Shrestha et al. (see references) decided to combine trap crops and insectary plants together with the cash crops in a strategy that they called a ‘botanical triad’. The cash crap was organic cabbage (Brassica oleracea var. capitata) planted in the eastern United States; the trap crops were three other crops of the genus Brassica: mighty mustard (Brassica juncea), kale (Brassica oleracea var. acephala) and collard (Brassica oleracea var. italica); and the insectary plants were buckwheat (Fagopyrum esculentum) and sweet alyssum (Lobularia maritima).
As a result, the number of herbivores (i.e., crop pests) was larger in the trap crops than in the cash crop. The trap crops were, therefore, more attractive than the cash crops for the pests. The presence of insectary plants increased the number of predatory and parasitoid insects, such as lady beetles and parasitoid wasps, in the trap crops when compared to treatments without insectary plants. The number of parasitized pests also increased in the presence of insectary plants.
In general, the “team work” of trap crops and insectary plants greatly reduced the influence of agricultural pests on the cash crops. The trap crops attracted the pests to an area close to the insectary plants, allowing the predators to reach them.
Efficient ways to raise crops organically are possible. We just have to focus on a healthy ecosystem and not on money. If we work together, we can defeat the “Big 6” corporations that dominate the food production in the world. They are the real pests.
It’s been a very long time since the last time I presented a lepidopteran here, so today I decided to go back to this amazing group of insects. The species I chose for today is quite popular, maybe the most popular moth in the world. Its name is Actias luna, commonly known as the luna moth.
The luna moth is native from Canada and the United States. It is a quite large moth, with a wingspan of about 8 to 12 cm, although some individuals can be as big as 18 cm. Its wings, covered with scales as usual in lepidopterans, have a light green color. The forewigs have a brown anterior border that connects to two eyespots (one on each wing) by a stalk. The hindwings also have one eyespot each, but they are not connected by a stalk to the border. The hindwings also have a long tail that is characteristic of the genus Actias and somewhat resembles the similar (but shorter) tails in some butterflies, such as those of the family Papilionidae. Males and females are very similar and can be often distinguished by the size of the abdomen, which is much thicker in females.
In colder climates, such as in Canada, the luna moth has one generation per year, but southern populations, in places where the climate is warmer, can have up to three. The females lay eggs on suitable plants to serve as food for the larvae. There are several identified tree species that are used as food, including birches, walnuts, hickories and persimmons. The larvae feeding on a tree never, or very rarely, reach a number that can cause significant damage to the plant.
The eggs are brown and laid in irregular clusters on the underside of the leaves. They usually hatch one to two weeks after being laid and originate small, green larvae. The larvae are green in all instars and pass through five of them during a period of about 7 weeks. The fifth and final instar then descends the tree in which it lives to reach the ground. There, it starts to spin a silk coccoon and, after finishing it, turns into a pupa. In warmer regions, the pupa takes about two weeks to become an adult, but in colder regions it enters into diapause over winter, taking about nine months to complete the cycle.
When females become adults, they search for a suitable tree of its preferred species (usually the same species in which it was born) and emits pheromones to attract males. Adults lack mouth parts and, therefore, do not eat, living only enough to mate and lay eggs. The nice long tails on the hindwings, more than just beautiful, seem to decrease the ability of bats to detect them using their echolocation.
The luna moth is one of the most popular insects in North America. In fact, it was the first insect ever to be described from the continent, being named Phalaena plumata caudata by James Petiver in 1700. When Linnaeus started the binomial nomenclature for animals in 1758, he renamed it Phalaena luna as a reference to the Roman goddess of the moon.
Although not considered a vulnerable species at the moment, the luna moth faces some threats caused by human interference, such as habitat loss and damage caused by invasive species. Fortunately, due to its popularity, it is likely to have considerable support from the public for its conservation when that time comes.
During the past three weeks, I presented a fig tree, the Chinese Banyan, a thrips that parasitizes it, the Cuban Laurel Thrips, and a mite that parasitizes the thrips, the Cuban-Laurel-Thrips Mite. However, I haven’t wrote yet about one of the most interesting creatures that interacts with a fig tree: its pollinator.
In the case of the Chinese Banyan, its pollinator is the fig wasp Eupristina verticillata, which I named the Chinese Banyan Wasp. As all fig wasps, this species is very small and completely adapted to live with figs. They cannot survive without the exact fig species with which they interact and the fig species cannot reproduce without that exact wasp. How does this works?
Let’s start our story with an adult female Chinese banyan wasp. The females are black and very small, measuring around 1 to 1.2 mm in length only. This female is flying around looking for a young fig which will serve as her nest and her grave.
A fig, in case you don’t know, is not a real fruit in the botanical sense. It is actually a special kind of inflorescence called a syconium that is basically a flower-filled sack. The inner walls of a fig have many tiny male and female flowers and the only way to get to them is through a tiny hole at the fig’s appex. And this hole is only open during the initial stages of the fig’s development.
When the female Chinese Banyan fig wasps is flying around, she is looking for a fig that is at this exactly stage of development. Once she finds one, she crawls inside the fig through that tiny hole. She usually loses her wings while doing that because the passage is too narrow. She evens needs to use her especially adapted mandible to help her go through. Once inside the fig, she looks for the female flowers, which are located at the base of the fig, away from the entrance. The male flowers, located right at the entrance, are not mature yet. However, the female wasps arrived with pollen that she gathered elsewhere (you will learn about that soon). When she reaches the female flowers, she introduces her ovopositor (the long structure at the end of her abdomen that is used to lay eggs) inside the female flower and lays one egg inside the flower’s ovary. Her ovopositor needs to have the exact size to reach the ovary to lay the egg. If it is too short, she is unable to complete her task. And while she is moving from flower to flower to lay eggs, she ends up pollinating them. After she has finished, she dies still inside the fig.
The ovaries that received an egg start to grow into a gall (a “plant tumor”) by influence of the insect and serve as food and shelter for the larvae that hatch from the eggs. A larva grows, pupates and turns into an adult inside a single gall. When the wasps have finally reached their adult stage, they leave the gall in which they were born. This happens when the fig reached its mature stage.
Males are the first ones to emerge. They are even smaller than the females and have a yellow to light-brown color. They gnaw their way through the gall and, once outside it (but still inside the fig) they start to look desperately for female wasps to inseminate. They do that by tearing other galls apart and, when a female is found trapped inside, they inseminate her. After that, the males dig a hole through the fig to the outside and die soon after, never experienced the external world.
Female wasps then leave their galls and move towards the hole opened by the male. While doing that, they move over the now mature male flowers and become covered in polen. After leaving the fig, they search for another fig that is in its early stage of development, restarting the cycle.
When a female leaves a mature fruit, she needs to find an immature one soon after that because she will die in a couple of days. In other words, the only way for this to work is if there are figs in the right stage all year around, and that is what happens. Differently from most plant species, which produce flowers in a specific time of the year, fig trees are always flowering. Well, not exactly. One individual fig tree produces figs only in a specific period of the year. All the figs of that tree ripen at the same time, i.e., a fig tree has an intra-individual synchrony of flower maturation. However, other trees of the same species have different moments to produce flowers, i.e., there is an inter-individual asynchrony of flower maturation. This assures that a wasp will always find a fig at the suitable maturation stage when there are enough fig trees around and also assures that a fig tree will not be fertilized by its own pollen.
As I mentioned when I presented the Chinese Banyan, this tree can only produce viable figs when the wasp is present, so that populations introduced outside of their native range will only reproduce if the waps is introduced as well. However, the wasp will be unable to survive if there are not enough fig trees to provide it with figs all year round. It is a delicate relationship between a tiny, fragile and short-lived insect and a huge, resistant and long-lived tree. And they need each other to survive.
McPherson JR (2005) A Recent Expansion of its Queensland Range by Eupristina verticillata, Waterston (Hymenoptera, Agaonidae, Agaoninae), the Pollinator of Ficus microcarpa l.f. (Moraceae). Proceedings of the Linnean Society of New South Wales: 126: 197–201.