Category Archives: Entomology

Friday Fellow: Yellow Mayfly

by Piter Kehoma Boll

Mayflies make up the order Ephemeroptera, one of the oldest ones among insects. Closely related to dragonflies and damselflies (order Odonata), mayflies have an aquatic nymph and a terrestrial imago (i.e., adult). One considerably well-known species is Heptagenia sulphurea, commonly known as the yellow mayfly or yellow may dun.

Native from Europe, the yellow mayfly lives most of its life as a nymph. It prefers running and clean waters, where it lives under stones and feeds on decaying plant matter and associated bacterial biofilms. The nymph has a flattenned body of a dark color with several yellowish marks. The legs are short and white and have a series of alternating yellow and black sinuous transversal stripes. Like in all mayfly nymphs, the abdomen has visible gills on both sides and three longe cerci (tails) at the tip. During its final stage as a nymph, the yellow mayfly is about 1 cm long.

Nymph of the yellow mayfly. Credits to European Fly Angler.

Most mayflies are very sensitive to pollution and the yellow mayfly is one of the most sensitive of all, at least in Europe. Whenever the water of a streams starts to get polluted, the yellow mayfly is the first mayfly species to disappear. Thus, its presence indicates water of very good quality.

Female subimago in Russia. Photo by Robin Bad.*

Different from all other insects, mayflies have an intermediate stage between the nymph and the imago stages, the so-called subimago. This stage is already terrestrial like the imago and already has wings, although they are often less developed, making them poor fliers. This subimago stage is commonly known as dun and, in the yellow mayfly, it has a typical yellow color, hence the common name yellow may dun. Females have black and poorly developed eyes, while in males the eyes are larger and vary from dark gray to whitish. Nymphs molt into subimagos beginning in May, when the peak occurs, but may appear as late as July.

Male imago of the yellow mayfly in Russia. Photo by Vladimir Bryukhov.*

When the subimago molts into the adult, usually after only a few days, the body becomes light brown and the eyes whitish in both sexes, but the eyes are still smaller in females than in males. Adults have the sole purpose of reproducing and so they do. After mating, the male dies in a few hours, and so does the female after laying her eggs in a stream.

The yellow mayfly is often used as a fishing bait. Once a common species across Europe, its populations have decreased considerably in the last century due to the increase of water pollution. Some recent efforts to despolute streams may, fortunately, help this and other mayfly species to find again more room to thrive.

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References:

Beketov MA (2004) Different sensitivity of mayflies (Insecta, Ephemeroptera) to ammonia, nitrite and nitrate between experimental and observational data. Hydrobiologia 528:209–216.

Macan TT (1958) Descriptions of the nymphs of the British species of Heptagenia and Rhithrogena (Ephem.). Entomologist’s Gazette 9:83–92.

Madsen BL (1968) A comparative ecological investigation of two related mayfly nymphs. Hydrobiologia 31:3–4.

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*Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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Friday Fellow: Black-Tipped Leafhopper

by Piter Kehoma Boll

The first fellow of 2020 is found in the forests, gardens and plantations of Southeast and East Asia. A member of the small insects commonly known as leafhoppers, its scientific name is Bothrogonia ferruginea and its common name is black-tipped leafhopper.

Leafhoppers belong to the order Hemiptera and feed on the sap of several plant species. The black-tipped leafhopper measures a little more than 1 cm as an adult. The dorsal color is yellow, a little greener on the wings than on the head and the thorax, and there is a group of black spots on the head and thorax, as well as a black margin at the posterior end of the forewings. The eyes are black an the legs are also yellow, with black areas at the joints. Some specimens may have a more orange tinge, from which the name ferruginea (rust-colored) must have come from. The ventral side is black with a yellow border in each segment.

Bothrogonia ferruginea in Japan. Photo by Wikimedia user Keisotyo.*

Eggs are elongate, greenish and small are laid in small clutches in the spring. The first-instar nymphs, which are small and white, hatch from the eggs after about 8.5 days. They develop into adults after about 2 months, passing through 4 more nymph instars. Adults are at first immature and live for 10 months. They slowly develop their sexual organs during summer and autumn, hibernate during four month in winter, and wake up from hibernation in spring, ready to mate.

Nymph of the black-tipped leafhopper in Taiwan. Photo by iNaturalist user nicolle10.**

Male black-tipped leafhoppers attach their sperm to a rope-like transparent material and transfer it to the females inside a large spermatophore, which is placed in their bursa copulatrix. Part of the material inside the spermatophore seems to be transferred into the eggs, as if it was some sort of nutritional gift of the father to his future kids.

It has been suggested that the peculiar color pattern of the black-tipped leafhopper is a form of mimetism. Their yellow background with black spots resembles the color pattern of ladybug pupae. Since ladybugs contain some toxins that makes them an unpleasant meal, imitating them helps the black-tipped leafhopper to be avoided as a food by many predators.

Two black-tipped leafhoppers in Taiwan. Photo by iNaturalist user nicolle10.**

As the black-tipped leafhopper feeds on several plant species, it can be a threat to some crops, especially grapes and tea. More than only feeding on the plants sap, the black-tipped leafhopper can be a vector to transmit the bacterium Xylella fastidiosa between plants. This bacterium is responsible for many plant diseases, including the Pierce’s disease of grapes, which leads to shriveled fruits and premature death of leaves.

Fortunately, the black-tipped leafhopper is not (yet) a major threat to any crop so there is no urge in studying their life history in details.

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More Hemipterans:

Friday Fellow: Pea Aphid (on 12 June 2015)

Friday Fellow: Southern Green Stink Bug (on 10 May 2019)

Friday Fellow: Wattle Horned Treehopper (on 23 August 2019)

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References:

Hayashi F, Kamimura Y (2002) The potential for incorporation of male derived proteins into developing eggs in the leafhopper Bothrogonia ferruginea. Journal of Insect Physiology, 48(2), 153–159. doi: 10.1016/s0022-1910(01)00159-7 

Tuan SJ, Hu FT, Chang HY, Chang PW, Chen YS, Huang TP (2016) Xylella fastidiosa transmission and life history of two cicaellinae sharpshooters, Kolla paulula and Bothrogonia ferruginea (Hemiptera: Cicadellidae), in Taiwan. Journal of Economic Entomology 109(3): 1034-1040. doi: 10.1093/jee/tow016

Yamazaki K (2010) Leafhopper’s face mimics the ladybird pupae. Current Science 98(4): 487–488.

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*Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

**Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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Friday Fellow: Hippo Fly

by Piter Kehoma Boll

If you ever lived in the countryside or visited the country side often, you may be aware of the existence of an annoying group of flies that bite humans and other animals, the so-called horseflies that make up the family Tabanidae. Today’s fellow is a member of this family and is known scientifically as Tabanus biguttatus and commonly as the hippo fly.

This species is found throughout Africa and some areas of Middle East, being, apparently, much more common in eastern and southeastern Africa. As with all tabanid flies, the hippo fly has an aquatic to semiaquatic larva that lives in muddy areas. They are ferocious predators and prey on other animals living in the same habitat, such as larvae of crane flies, and can also feed on dead animals. When the larvae are about the pupate, they construct a mud cylinder, cover it with a circular lid with only a small hole to allow them to breathe, and remain there until they turn into adults. This is, apparently, a strategy to avoid desiccation.

Male hippo fly in South Africa. Photo by Ryan Tippett.*

Adult hippo flies measure about 2 cm in length, being relatively large tabanids, and show a considerable sexual dimorphism. As all tabanids, males are smaller but have larger compound eyes than females. The eyes of the males are so large that they touch each other, covering the whole top of the head. Females, on the other hand, have smaller eyes with a considerable space between them. The body of both males and females is predominantly black. Males have two white triangular spots on the abdomen while females have the thorax covered with white to golden hair with a small heart-shaped black spot in the middle.

Female hippo fly in South Africa. Photo by iNaturalist user bgwright.*

Male adult hippo flies are harmless and feed only on nectar. Females, on the other hand, need mammal blood to obtain enough protein for egg development. They attack many large mammal species, including humans, cattle and even dogs, but they have a strong preference for hippos, hence the common name.

Two female hippo flies feeding on a southern warthog (Phacocerus africanus spp. sundevallii). Photo by iNaturalist user happyasacupake.*

Hippo flies, like all tabanids, are diurnal flies and love sunny places. They avoid shaded areas, so animals in open areas are much more vulnerable. To get blood, a female approach animals and cut their skin with her sharp mouthparts, making them bleed and licking up the blood. This bite is very painful, which you may know if you have ever been bitten by a horsefly. If undisturbed, the fly can remain up to three minutes drinking blood.

Closeup of the two flies on the warthog’s back. Photo by iNaturalist user happyasacupake.*

The blood-drinking activity of female hippo flies, and of tabanids in general, make them likely mechanical vectors of some parasites, including species of the flagellate genus Tripanossoma, as well as Bacillus anthracis, the bacteria that causes anthrax, which is a considerably common disease in hippos.

Hippo flies are such a nuisance for hippos that their behavior is heavily affected by the flies’ presence, much more than by the presence of any large predator. Most of the time, hippos remain in the water solely to get rid of these annoying insects.

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More Dipterans:

Friday Fellow: Housefly (on 12 October 2012)

Friday Fellow: Cute Bee Fly (on 29 July 2016)

Friday Fellow: Bathroom Moth Midge (on 5 April 2019)

Friday Fellow: Blue Paddled Mosquito (on 27 September 2019)

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References:

Callan EM (1980) Larval feeding habits of Tabanus biguttatus and Amanella emergens in South Africa (Diptera: Tabanidae). Revue de Zoologie Africaine 94(4): 791-794.

Tinley KL (2009) Some observations on certain tabanid flies in North-Eastern Zululand (Diptera: Tabanidae). Proceedings of the Royal Entomological Society of London. Series A, General Entomology, 39(4-6), 73–75. doi: 10.1111/j.1365-3032.1964.tb00789.x

Tremlett JG (2009) Mud cylinders formed by larvae of Tabanus biguttatus Wied. (Diptera: Tabanidae) in Kenya. Proceedings of the Royal Entomological Society of London. Series A, General Entomology, 39(1-3), 23–24. doi: 10.1111/j.1365-3032.1964.tb00779.x

Wiesenhütter E (1975) Research into the relative importance of Tabanidae (Diptera) in mechanical disease transmission. Journal of Natural History, 9(4), 385–392. doi: 10.1080/00222937500770281 

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Friday Fellow: Emerald Ash Borer

by Piter Kehoma Boll

It’s time for our next beetle and this time our fellow is a species that spent its first century after discovery without calling much attention but then something happened. Its name is Agrilus planipennis and is commonly known as the emerald ash borer.

An adult emerald ash borer in Virginia, USA. Photo by Bryan Wright.*

Native from East Asia, the emerald ash borer is found in southeastern Russia, Mongolia, northern China, Korea and Japan. Adults measure about 8.5 mm in length and have a metalic green color on the head, pronotum and elythra, and an iridescent-purple metalic color on the dorsal side of the abdomen, seen when the wings are open. They live in the canopy of ash trees (Fraxinus spp.) during spring and summer and feed on their leaves.

After about a week as adults, the emerald ash borers start to mate. Females remain on the trees and males hover around looking for them. Once a female is located, the male drops over her and they start to mate. After mating is concluded, females live for some more weeks and typically lay about 40 to 70 eggs, although some live longer and may lay up to 200 eggs.

Dorsal view of an emerald ash borer with open wings showing the iridescent-purple abdomen.

The eggs are laid between crevices or cracks of the bark and hatch about two weeks later. The newly hatched larvae chew through the bark, reach the inner tissues of the trunk and start to feed on them. They reach up to 32 mm in length in the fourth instar, more than three times the length of the adult, and pupate during spring, emerging as adults soon after. In China, adults emerge from the trees in May.

A larva inside an ash tree in Pennsylvania, USA. Credits to the Pennsylvania Department of Conservation and Natural Resource.**

In its native area, the emerald ash borer can be a nuisance but is not highly problematic to ash trees because it occurs in low densities. However, in 2002, the species was found in the United States feeding on local ash species. Since the emerald ash borer has no natural predators in North America and the ash species in this continent did not evolve to be resistant to infection, it started to spread very quickly. In less than two decades, the beetle has killed millions of ash trees and is a serious threat to the more than eight billion ash trees found in North America. With the death of ash trees, North American forests become vulnerable to more invasive species, which will only worsen the scenario.

Damage caused by the larvae to a tree in New York state, USA. Photo by iNaturalist user bkmertz.*

In order to control the spread of the emerald ash borer, ash trees are treated with pesticides. Four parasitoid wasps from China known to attack only the emerald ash borer have also been released in North America to help control the spread and their success is still being assessed. Traps, such as glue-covered purple panels, which are visually attractive to the beetles, are also used to capture the animals and determine the extent of the invasion.

Once more, a completely fine species has led to an ecological disaster due to human influence and now we are running to find ways to avoid an ecosystem collapse throughout an entire continent.

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References:

Francese JA, Mastro VC, Oliver JB, Lance DR, Youssef N, Lavallee SG (2005) Evaluation of colors for trapping Agrilus planipennis (Coleoptera: Buprestidae). Journal of Entomological Science 40(1): 93-95.

Liu H, Bauer LS, Miller DL, Zhao T, Gao R, Song L, Luan Q, Jin R, Gao C (2007) Seasonal abundance of Agrilus planipennis (Coleoptera: Buprestidae) and its natural enemies Oobius agrili (Hymenoptera: Encyrtidae) and Tetrastichus planipennisi (Hymenoptera: Eulophidae) in China. Biological Control 42(1): 61-71. doi: 10.1016/j.biocontrol.2007.03.011

Wang XY, Yang ZQ, Gould JR, Zhang YN, Liu GJ, Liu ES (2010) The biology and ecology of the emerald ash borer, Agrilus planipennis, in China. Journal of Insect Science 10(1): 128. doi: 10.1673/031.010.12801

Wikipedia. Emerald ash borer. Available at < https://en.wikipedia.org/wiki/Emerald_ash_borer >. Access on 9 December 2019.

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**Creative Commons License This work is licensed under a Creative Commons Attribution 3.0 Unported License.

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Friday Fellow: Cherry Spot

by Piter Kehoma Boll

Butterflies and moths, the insects that make up the order Lepidoptera, have a relationship of love and hatred with flowering plants, since their caterpillars feed voraciously on plant tissues but the adults are important pollinators.

In Sub-Saharan Africa, from Cameroon to South Africa, a relatively common lepidopteran is Diaphone eumela, known as the cherry spot. This species belongs to the family Noctuidae, one of the most diverse families of moths.

A caterpillar with its typical color. Photo by Felix Riegel.*

The caterpillars feed on several plants of the family Amaryllidaceae and have a yellow to light green background color. Each segment of the body has some pale orange spots that are surrounded and connected by a black area, forming a series of irregular rings. The head is orange and the orange spot of the first thoracic segment and the last abdominal segment are darker than in the rest of the body.

When it’s time to pupate, the caterpillar buries itself in the ground and makes an earth coccoon, inside of which it molts into a brown pupa. About three weeks later, the pupa turns into an adult.

A caterpillar about to turn into a pupa inside the coccoon (left) and two pupae (right). Photo by Sally Adam.*

The adult is a beautiful creature. The thorax is covered by gray hair with six yellow spots. The forewings have a gray and white background and three transversal black lines crossing them. Connected to the posteriormost line, there is a red spot with a cherry-red tinge, hence the common name. Along the outer border of the forewings, there’s a yellow line interrupted by gray projections of the background color. The hindwings, often hidden under the forewings, are fully white and the abdomen, also hidden most of the time, has yellow and black rings as a reminescent of the caterpillar.

A beautiful adult. Photo by Sally Adam.*

I was not able to find much information about the life history of this species. By analyzing photographs on iNaturalist, adults seem to emerge between August and December. The females tend to lay eggs on plants whose flowers are starting to open and the young caterpillars feed preferentially on flower buds. Older caterpllars, on the other hand, feed mainly on the fruits produced by the flowers that they did not devoured early in life.

Although beautiful and conspicuous, the cherry spot is still surrounded by many mysteries. We only need someone interested in studying them.

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References:

Stirton CH (1976) Thuranthos: notes on generic status, morphology, phenology and pollination biology. African Biodiversity & Conservation 12(1): a1389. doi: 10.4102/abc.v12i1.1389

Wikipedia. Diaphone eumela. Available at < https://en.wikipedia.org/wiki/Diaphone_eumela >. Access on October 22, 2019.

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Friday Fellow: Black Stonefly

by Piter Kehoma Boll

Insects are so diverse that it will take quite a time to present all groups here. Today I am going to show you the first species of the order Plecoptera, commonly known as stoneflies. Our species is named Austroperla cyrene and commonly known as the black stonefly.

The black stonefly is endemic to New Zealand, being found in both North Island and South Island. The adults measure about 1.5 cm in length and have a black body with black wings. The only part of the body that is not black or very dark brown is a yellowish region on each leg and at the base of the forewings. Males tend to be smaller than females.

Adult black stonefly in the North Island. Photo by Erin Powell*.

As common among many adult insects, adult black stoneflies rarely eat but they prefer plant matter when necessary. They live only a few weeks, enough time to mate and start laying their eggs. The females lay the eggs in streams and the nymphs are aquatic, with a dark brown body and two very short cerci (“tails”). The nymphs feed on dead plant matter, such as rotten wood and dead leaves, and can also feed on dead animals or fungi growing on dead plant matter. They take about three years to become adults. Most nymphs leave the water and molt into adults from late spring to late summer.

A nymph captured in the South Island. Photo by iNaturalist user anna-mac.*

Both nymph and adult black stoneflies have some amount of hydrogen cyanide in their tissues. As a result, they are avoided by both aquatic and terrestrial predators. The yellow marks on the adult may serve as a warning about the species’ toxicity and unpalatability, telling predators to stay away or face the consequences of a very unpleasant meal.

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References:

McLellan, ID (1997) Austroperla cyrene Newman (Plecoptera: Austroperlidae). Journal of the Royal Society of New Zealand 27(2): 271–278. doi: 10.1080/03014223.1997.9517538

Thomson MS (1934) An account of the systematics, anatomy and bionomics of Austroperla Cyrene Newman. Master Thesis, Canterbury University.

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Filed under Entomology, Friday Fellow, Zoology

Friday Fellow: Eucalyptus Gall Wasp

by Piter Kehoma Boll

Galls are a common abnormal growth on plant tissues, being similar to animal warts, and can be caused by several different parasites, including viruses, bacteria, fungi, arthropods and sometimes even other plants. Sometimes galls can be harmless but they are often able to affect the plant’s fitness to a degree that harms it.

In several species of eucalyptus, including the river red gum presented here last week, a common agent causing galls is Ophelimus maskelli, known as the eucalyptus gall wasp. As its name suggests, this species is a wasp, more precisely a chalcid wasp, therefore related to several parasitoid wasps and the fig wasps.

An adult female eucalyptus gall wasp. Extracted from https://bicep.net.au/pests/ophelimus-maskelli/

The eucalyptus gall wasp is very small, measuring, as an adult, only about 1 mm in length and having a black body. After mating, the female looks for immature eucalyptus leaves, 15–90 days old, growing in the lower tree canopy because leaves are larger there. A female lays about 100 eggs and has a preference for the area close to the leaf’s petiole. As soon as the eggs are laid, a reaction on the leaf tissues leads to the formation of the galls, with one larva growing inside each gall. In heavily infested trees, the whole leaf can be covered and there may be as much as 36 galls per cm². The larva pupates inside the gall and leaves after reaching the adult stage.

A heavily infested eucalyptus leaf with numerous galls. Credits to NHMLA Community Science Program.**

After the adults emerge, the leaves start to desiccate, especially the heavily infested ones, and die, weakening the tree. As a result, the eucalyptus gall wasp is considered a serious eucalyptus pest and can have devastating effects on eucalyptus plantations.

The eucalyptus gall wasp is native from Australia, since most eucalyptus species come from there, but was accidentally introduced in several other countries together with the eucalyptus trees, especially in the last decades. The galls are easily identified as very small, somehow oval eruptions, not very tall, seen from both the upper and lower sides of the leaf. After the adult emerge, there is a visible hole on the gall and the surroundings start to dry.

Several methods to reduce the infections are used, including pesticides and biological control, especially of other chalcid wasps such as the parasitoid Closterocerus chamaeleon. Considering that this pest is a relatively novel nuisance in a global scale, effective control methods are still being developed.

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More hymenopterans:

Friday Fellow: Bullet Ant (on 27 May 2016)

Friday Fellow: Jataí Bee (on 12 August 2019)

Friday Fellow: Turnip Sawfly (on 17 May 2019)

Friday Fellow: Chinese Banyan Wasp (on 5 July 2019)

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References:

Branco M, Boavida C, Durand N, Franco JC, Mendel Z (2009) Presence of the Eucalyptus gall wasp Ophelimus maskelli and its parasitoid Closterocerus chamaeleon in Portugal: First record, geographic distribution and host preference. Phytoparasitica 37(1): 51–54. doi: 10.1007/s12600-008-0010-7

Burks RA, Mottern JL, Waterworth R, Paine TD (2015) First report of the Eucalyptus gall wasp, Ophelimus maskelli (Hymenoptera: Eulophidae), an invasive pest on Eucalyptus, from the Western Hemisphere. Zootaxa 3926(3): 448–450. doi: 10.11646/zootaxa.3926.3.10

Dhahri S, Ben Jamaa ML, Lo Verde G (2010) First record of Leptocybe invasa and Ophelimus maskelli eucalyptus gall wasps in Tunisia. Tunisian Journal of Plant Protection 5: 231–236.

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