Monthly Archives: February 2020

Friday Fellow: Reddish Cuckoo Wasp

by Piter Kehoma Boll

Besides the well-known internal and external parasites that feed on resources of the host, nature has other types of parasitism as well. One of those types is the so-called brood parasitism, in which an animal puts its eggs in the nest of another animal so that they will be raised by foster parents, usually from a different species. Cuckoos are certainly the most famous brood parasites, laying their eggs in the nests of other birds.

But brood parasites exist among other animal groups as well, including, of course, the diverse order Hymenoptera. Wasps of the family Chrysididae are known as cuckoo wasps because they put their eggs in the nests of other wasps. One species of this family is Hedychrum rutilans, which I decided to call the reddish cuckoo wasp.

A reddish cuckoo was in the Netherlands. Photo by iNaturalist user v_s_*.

Adults of this species measure up to 1 cm in length and have a kind of ant-shaped body. Its most striking feature, however, is its metalic color, which is typical of cuckoo wasps. In the reddish cuckoo wasp, the abdomen and the front part of the thorax have a reddish tinge, while the rest of the body is somewhat green.

Living in Europe and the northermost regions of Africa, the reddish cuckoo wasp is a lovely nectar drinker as an adult. However, as a larva, it is a parasitoid. Females put their eggs inside another insect so that the larva feeds on the host from inside. However, as I mentioned, cuckoo wasps are brood parasites, hence the name cuckoo wasp. Thus, they do not hunt other insects to serve as hosts for their larvae. Instead, they invade the nests of another species, the European beewolf, which I presented last week, and lay their eggs on the bees that the European beewolf has hunted for its own offspring.

Reddish cuckoo wasp in France. Photo by iNaturalist user butor*.

When the egg of the reddish cuckoo wasp hatches, the larva starts to feed on the paralyzed bees and can even feed on the growing larvae of the beewolf. But how can the female cuckoo wasp manage to invade the beewolf’s nest without being noticed?

The surface of insects is covered by cuticular hydrocarbons (CHCs), which have several functions. They protect the body from water and have many functions for chemical communication, both intra- and interspecifically. Parasitoids, for example, rely on CHC cues to find their hosts, and many species, especially social insects such as bees and ants, use CHCs to recognize individuals of their own colony and to detect any invader, incluing parasitoids and brood parasites. Thus, a beewolf could easily locate a cuckoo wasp sneaking into its nest but natural selection made the necessary changes. The amount of CHCs on the surface of cuckoo wasps is way below the normal levels found in most insects. As a result, their smell is so weak that it cannot be perceived in a nest that reeks of beewolf CHCs.

A specimen in Russia. Photo by Shamal Murza.*

One strategy that beewolfs seem to have developed to reduce the levels of parasitism by the reddish cuckoo wasp is increasing their activity in the evening, when the cuckoo wasp activity is reduced. During this time, it is easier for beewolves to enter their nests without being detected by cuckoo wasps. When a beewolf detects a cuckoo wasp close to its nests, it attacks it ferociously. However, once a cuckoo wasp enters the nest, the beewolf is unable to recognize it even if running right into it due to its inability to chemically detect the invader.

Both parties, of course, will always try to find new ways to succeed. Nature is, afterall, a neverending arms race.

– – –

Like us on Facebook!

Follow us on Twitter!

– – –

References:

Kroiss J, Schmitt T, Strohm E (2009) Low level of cuticular hydrocarbons in a parasitoid of a solitary digger wasp and its potential for concealment. Entomological Science 12:9–16. doi: 10.1111/j.1479-8298.2009.00300.x

Kroiss J, Strohm E, Vandenbem C, Vigneron J-P (2009) An epicuticular multilayer reflector generates the iridescent coloration in chrysidid wasps (Hymenoptera, Chrysididae). Naturwissenschaften 983–986. doi: 10.1007/s00114-009-0553-6

Strohm E, Laurien-Kehnen C, Boron S (2001) Escape from parasitism: spatial and temporal strategies of a sphecid wasp against a specialised cuckoo wasp. Oecologia 129:50–57. doi: 10.1007/s004420100702

– – –

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

Leave a comment

Filed under Entomology, Friday Fellow, Zoology

Friday Fellow: European Beewolf

by Piter Kehoma Boll

Among the species of the highly diverse insect order Hymenoptera, many are known to be parasites or parasitoids of a variety of animals and plants. Commonly known parasited species include spiders and caterpillars, but some hymenopterans parasitize other hymenopterans.

One of such species is Philanthus triangulum, known as the European beewolf. The name beewolf refers to the fact that this wasp species hunts bees, particularly the common honey bee Apis mellifera. This species occurs throughout Europe and Africa, having several subspecies.

A female European beewolf in Gran Canaria, Spain. Photo by Juan Emilio.**

The European beewolf has about the same length as its prey, the common honey bee, but its body has a more typical wasp look. The abdomen and the legs are predominantly yellow, while the head and the thorax are mainly black and brown. The yellow abdomen has black transversal stripes that are typical in many wasp species but their width can vary. Males are smaller than females and have a characteristic trident-shaped light mark between the eyes that is absent or very small in females.

A male in Andalucia, Spain. See the trident-shaped mark between the eyes. Photo by flickr user gailhampshire.*

In colder regions, where the winter is harsh, adult European beewolves emerge as adults in early summer. Both male and female adults feed on the nectar of several plants. Females create large and sometimes complex burrows in sandy soils in open sunny places. The burrows may have up to a meter in length and have between 3 and 34 short tunnels, the brood cells, at the end, each of which will be used to raise one larva. Once finishing the burrow, the female searches for honeybees to hunt. When attacking the bee, the beewolf stings it behind the front legs and paralyzes it, and then flies back to the nest carrying the paralyzed bee below her between her legs. Up to five honeybees can be provided for each larva and serve as their only food during their development.

A female with a paralyzed bee in England. Photo by Martin Cooper.*

Males tend to live near female burrows and use sex pheromones to attract them. Although they are territorial, they can sometimes tolerate other males nearby because the increased release of feromones increases the chances of them being detected by the females.

After the female has provided each egg with enough food, it closes the burrow and leaves. However, since the larvae will remain several months in that closed and humid environment, they can end up suffering from mold growth that can destroy themselves or their food. Females seem to have developed several strategies to reduce this problem. First, before laying the egg on the bee, the wasp licks most of the bee’s surface, applying a secretion from a postpharyngeal gland. Although this secretion has no antimycotic properties, it seems to delay water condensation on the bee’s surface, which also delays the development of fungi, and at the same time prevents water loss from the bee’s body, ensuring that the larvae will have the necessary amount of water to survive.

Carrying a bee into the burrow in England. Photo by Charlie Jackson.*

Female beewolves also live symbiotically with bacteria of the genus Streptomyces, which they cultivate in specialized glands in their antennae. They “secrete” the bacteria into the brood cells before leaving and later, when the larvae hatch, they collect the bacteria and apply them on the surface of a coccoon that they build to overwinter. These bacteria thus prevent fungi or other bacteria from growing on the coccoon, protecting the larvae from infections.

Nature never stops amusing us with its wonderful strategies so beautifully built by natural selection.

– – –

Like us on Facebook!

Follow us on Twitter!

– – –

References:

Herzner G, Schmitt T, Peschke K, Hilpert A, Strohm E (2007) Food Wrapping with the Postpharyngeal Gland Secretion by Females of the European beewolf Philanthus triangulum. Journal of Chemical Ecology 33:849–859. doi: 10.1007/s10886-007-9263-8

Herzner G, Strohm E (2008) Food wrapping by females of the European Beewolf, Philanthus triangulum, retards water loss of larval provisions. Physiological Entomology 33:101–109. doi: 10.1111/j.1365-3032.2007.00603.x

Kaltenpoth M, Goettler W, Dale C, Stubblefield JW, Herzner G, Roeser-Mueller K, Strohm Erhard (2006) ‘Candidatus Streptomyces philanthi’, an endosymbiotic streptomycete in the antennae of Philanthus digger wasps. International Journal of Systematic and Evolutionary Microbiology 56: 1403–1411. doi: 10.1099/ijs.0.64117-0

Wikipedia. European beewolf. Available at < https://en.wikipedia.org/wiki/European_beewolf >. Access on 20 February 2020.

– – –

**Creative Commons License This work is licensed under a Creative Commons Attribution-Share Alike 2.0 Generic License.

*Creative Commons License This work is licensed under a Creative Commons Attribution 2.0 Generic License.

Leave a comment

Filed under Entomology, Friday Fellow, Parasites, Zoology

Friday Fellow: Asian Clam

by Piter Kehoma Boll

Since humans appeared on Earth and started to migrate, they carried other species with them to new localities. This made humans not the only species to become invasive and, in the past centuries, with human movement throughout the planet becoming more and more intense, invasive species became more and more common.

Among bivalvian mollusks, two very popular invasive species are the golden mussel and the zebra mussel, but they are not the only ones. There is one small bivalvian that is not that often a nuisance in human activities but is certainly a problem for native species, the so-called Asian clam, Corbicula fluminea.

An Asian clam in Hong Kong. Photo by Tommy Hui.*

The Asian clam is native from Eastern Asia where it lives burried in the sediment of rivers, prefering sandy sediments in oxygen-rich waters. Their small bivalvian shell measures up to 5 cm although most adult specimens are about 3 cm long. They have a brown to golden color, sometimes combined, but the colored layers sometimes flake off, causing white blotches.

The food of the Asian clam consists mainly of phytoplankton that it filters from the sediment. Human populations from Eastern Asia, such as the Chinese and Koreans, often use the Asian clam as a food source. During the 20th century, when many East Asian people migrated to other countries, the Asian clam was carried with them to be raised as food. As a result, this mollusk was introduced in North and South American river basins and started to spread quickly

The Asian clam is not as tolerant to environmental changes as other invasive bivalvians but its advantage is its rapid reproduction. Although there are both dioic and hermaphrodite lineages in this species, the invasive populations are all hermaphrodites. Fertilization occurs inside the body of the mother clam and the larvae develop inside, being released already as tiny shelled individuals.

The first records of this species in North America are from areas in the west coast of the United States in the 1920s. One century later the species is found throughout the whole country, having reached the east coast in less than four decades, and going north to Canada and south to Mexico and Central America.

Asian clam in Massachusetts, USA. Photo by iNaturalist user jfflyfisher.*

In South America, the species was introduced simultaneously in the La Plata River between Argentina and Uruguay and in the Jacuí river in southern Brazil in the 1970s. Currently, less than 50 years later, it is found as far north as Colombia as southward into Patagonia. The species was also introuced in Europe, Africa and Australia.

Shells collected in the La Plata River in Buenos Aires, Argentina. Photo by Diego Gutierrez Gregoric.*

The main impact caused by the invasion of the Asian clam is that it competes with native bivalvians, frequently leading to local extinctions, which is a major threat especially to many rare species that may disappear in a few decades. Although impacts on human activities are not that common, there are cases of large numbers of individuals clogging pipes and other structures.

A shell in Colombia. Credits to iNaturalist user gerardochs.*

Since there are fossil records of species of the genus Corbicula in North America, a hypothesis was raised suggesting that, instead of an invasion, the spread of the Asian clam in this continent is actually a recolonization following the last glaciation and that these individuals may be the result of small populations that remained hidden somewhere. However, it is very unlikely that the species would have remained hidden in very small populations for thousands of years to suddenly start to spread like hell in a few decades. Humans are to be blamed, as always.

– – –

Like us on Facebook!

Follow us on Twitter!

– – –

References:

Araujo R, Moreno D, Ramos MA (1993) The Asiatic clam Corbicula fluminea (Müller, 1774) (Bivalvia: Corbiculidae) in Europe. American Malacological Bulletin 10(1): 39–49.

Planeta Invertebrados. Corbícula. Available at < http://www.planetainvertebrados.com.br/index.asp?pagina=especies_ver&id_categoria=27&id_subcategoria=0&com=1&id=143 >. Access on 13 February 2020.

Sousa R, Antunes C, Guilhermino L (2008) Ecology of the invasive Asian clam Corbicula fluminea (Müller, 1774) in aquatic ecosystems: an overview. Annales de Limnologie 44(2): 85–94. doi: 10.1051/limn:2008017

– – –

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

Leave a comment

Filed under Friday Fellow, mollusks, Zoology

Friday Fellow: Aloe Mite

by Piter Kehoma Boll

Some months ago I introduced a tiny wasp that causes galls in eucalyptus trees. Now I am going to present another tiny creature, even smaller than that wasp, that causes a very abnormal type of gall in species of the genus Aloe.

Called Aceria aloinis and commonly known as the aloe mite, this microscopic arachnid can be a nightmare to aloe species and to those that cultive them. They are so tiny that they are barely seen with the naked eye. Their body is elongate and cylindrical, vermiform, like a microscopic sausage, and the adults have only four legs instead of the typical eight of most arachnids. This is the typical appearance of most mites of the family Eriophyidae, known as gall mites.

Two aloe mites. Extracted from Deinhart (2011).

Feeding on the epidermal cells of aloe plants, the aloe mite leads to a huge problem in its host. Its effect leads to an abnormal and ugly growth forming a shapeless gall that is adequately known as aloe cancer. This cancer often has a sponge-like appearance and sometimes, more than only strange growths from the leaves, stems and inflorescences, it can appear as a cluster of malformed leaves.

An ugly gall formed by the aloe mite. Photo by Colin Ralston.*

This malformation most likely has some negative effects on the plant’s fitness but the main concern is because it makes ornamental aloe species aesthetically unappealing. The most simple way to get rid of the aloe mite is to cut off the infected parts and burn them.

But how did they get to the plant in the first place? Well, eriophyid mites in general use the wind to be carried from one place to another and the aloe mite is no exception. So you may be able to cure your plant with an amputation but if there are other infected plants in the region, the mites may soon be back.

– – –

Like us on Facebook!

Follow us on Twitter!

– – –

References:

Deinhart N (2011) Tiny Monsters: Aceria alionis. Cactus and Succulent Journal 83(3): 120–122. doi: 10.2985/0007-9367-83.3.120

Villavicencio LE, Bethke JA, Dahlke B, Vander Mey B, Corkidi L (2014) Curative and preventive control of Aceria aloinis (Acari: Eriophyidae) in Southern California. Journal of Economic Entomology 107(6):2088-2094.

– – –

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

Leave a comment

Filed under Arachnids, Friday Fellow, Zoology