Tag: larvae

A provisional checklist of European butterfly larval foodplants

For the first time, a list of the currently accepted plant names utilised by 471 European butterfly larvae is presented, with references.

Guest blog post by Harry E. Clarke, Independent Researcher

5th instar Swallowtail larvae feeding on Milk-parsley.

Many books on butterflies publish lists of their larval foodplants. However, many of these lists of larval foodplants have been copied from previous lists, which in turn have been copied from previous lists. Consequently, errors have crept in, and many plant names have long been superseded. This can result in duplicates in the list, with the same plant being given two different names. Most plant lists do not include the authority, which can make it difficult or impossible to identify which plant is being referred to. Some of these plants may not be used by butterflies in Europe, but elsewhere in their range. Or the plants may have been used in breeding experiments, but not used by the butterflies in the wild.

Many of these publications providing the larval foodplants of butterflies only provide the binomial name, without specifying the author. This can create problems in knowing which species of plant is being used, as the same plant name has been used in the past by different authors to describe different species. In some cases, distribution can be used to determine the correct species, but plants can often have similar distributions. For example, in the World Checklist of Vascular Plants, there are 40 entries for the plant with the scientific name Centaurea paniculata, which refer to thirteen different accepted species, depending on authors, subspecies, and variety or form.

Not quite so simple: updating the current lists of larval foodplants

With climate change and habitat loss threatening numerous species, the conservation of butterflies (and other animals) is becoming more important. Whilst many factors determine the distribution of butterflies, such as temperature and rainfall, their survival depends solely on the kinds of plants their larvae eat. Accurate lists of larval foodplants are therefore important to find out where to direct limited conservation resources for the best result.

What started out as a straightforward job of updating the existing lists of larval foodplants with currently accepted names turned out to be a far bigger job. Many of the lists are incomplete, and may vary throughout the range of the butterfly. Here, errors have crept in too. Many references provide incomplete, unverifiable information. Many species of butterfly lay their eggs off-host, rather than on the host plant. For example, the Silver-washed Fritillary (Argynnis paphia)oviposits on tree trunks above where Viola species are growing. Consequently, oviposition records need to be treated with caution, depending on the species.

What do butterfly larvae eat, and why does it matter?

Butterfly larvae can be very fussy about which plants they can use. 20% of European butterfly larvae are monophagous, feeding on just one species of plant. 50% are oligophagous, feeding on a few different closely related plants, whilst 30% are polyphagous feeding on plants in many different families. The Holy Blue (Celastrina argiolus) can utilise plants in an astonishing 19 different families.

The oligophagous butterflies can be divided into two groups:

Oligophagous-monophagous (OM) – feeding on one plant species in one region, and another species in another region.
Oligophagous-polyphagous (OP) – feeding on several closely related species of plants throughout their range, usually in the same genus, or a closely related genus.

4th instar Small Tortoiseshell feeding on Common Nettle.

Plant preferences are only known for a few species of butterflies. For example, the English race of the Swallowtail (Papilio machaon) feeds on Milk-parsley (Peucedanum palustre), whereas in the rest of Europe it has been recorded on 62 other plants. The main larval foodplant of the Small Tortoiseshell (Aglais urticae) is Common Nettle(Urtica dioica), although it will occasionally use other plants.

The survivability of larvae on different plants is largely unknown, except in a few cases where the butterfly species has been studied in detail. There are plants that larvae may be able to eat, but that would likely not help them survive to pupation.

Two species are known to switch their larval foodplant during their second year of development. The Scarce Fritillary (Euphydryas maturna),for example, switches from Ash (Fraxinus excelsior) to Guelder-rose (Viburnum opulus). The Northern Grizzled Skipper (Pyrgus centaureae) switches from Dwarf birch (Betula nana) to Cloudberry (Rubus chamaemorus).

The most delicious plants

For the first time, a list of the current accepted plant names utilised by 471 European butterfly larvae is presented, with references. Where possible, errors in previous lists have been removed. The list of larval foodplants doubled compared to previous published lists. This has resulted in a list of 1506 different plant species in 72 different families. 86 plant records are only known at the generic level. Larval foodplants of 25 butterfly species are currently unknown, which are mostly the “Browns” (Satyrinae), which probably feed on grasses (Poaceae), or possibly sedges (Cyperaceae).

Whilst most plant families are utilised by less than six butterfly species, a few plant families are particularly favoured, with grasses (Poaceae) and legumes (Fabaceae) being the most popular. Similarly, most plant species are only utilised by a few butterfly species, but the fine grasses Sheep’s Fescue (Festuca ovina) and Red Fescue (Festuca rubra) are favoured by a large number of butterfly species.

Taxonomic splits create problems. Where cryptic species are allopatric, records can be allocated on the basis of their distribution. But where cryptic species are sympatric, this will require a resurvey to determine the larval foodplants. It cannot be assumed that two cryptic butterfly species use the same plants, as something has to become different for them to evolve into separate species.

Looking forward

Future publications should ensure that old and ambiguous plant names are not used. Plant names should be specified with their full scientific name, as specified by the International Code of Nomenclature for algae, fungi, and plants. The World Checklist of Vascular Plants should be checked to ensure the currently accepted plant name is being used.

Fully documented records are needed of what larval foodplants butterfly larvae are utilising in the wild. To get a better understanding of usage, full details need to be recorded, including date, location, altitude, abundance, and larval stage. Abundance will help in the understanding of preferences. To allow records to be properly verified, evidence should be provided on how the larvae and plants were identified. Regional lists are also important – to help direct conservation efforts to the plants being used locally, rather than elsewhere. This list of larval foodplants is provided as a step towards a fully justified database, which will be updated as and when corrections are found. It highlights those 25 butterfly species whose larval foodplants are currently unknown.

4th instar Chequered Skipper (Carterocephalus palaemon) larvae feeding on Purple Moor-grass (Molinia caerulea).

Research article:

Clarke HE (2022) A provisional checklist of European butterfly larval foodplants. Nota Lepidopterologica 45: 139-167. https://doi.org/10.3897/nl.45.72017

First moth species on Alpenrose discovered

Discovery of the first moth species to mine the leaves of the highly poisonous Alpine rose

Rust-red alpine rose, one of the most popular alpine plants. Photo by Ingrid Huemer

An Austrian-Swiss research team was able to find a previously unknown glacial relic in the Alps, the Alpine rose leaf-miner moth. It is the first known species to have its caterpillars specializing on the rust-red alpine rose, a very poisonous, widely distributed plant that most animals, including moths and butterflies, strictly avoid. The extraordinary record was just published in the peer-reviewed scientific journal Alpine Entomology.

Poisonous host plant

The rust-red alpine rose (Rhododendron ferrugineum) is among the best-known and most attractive plants due to its flowering splendor – at least for humans. It is, in fact, a highly poisonous plant, strictly avoided by grazing animals. For insects, the alpine rose is attractive at most as a nectar plant; insect larvae, on the other hand, develop on it only in exceptional cases. This also applies to Alpine butterflies and moths, which leave Alpine roses largely untouched despite their wide distribution. Therefore, the discovery of a highly specialized species in the Alps came as a complete surprise.

Chance find

Alpine rose leaf-miner moth adults resting on leaves of the host-plant in Ardez, Graubünden, Switzerland. Photos by Jürg Schmid

Since alpine roses are unattractive to caterpillars and no insect the entire Alpine region was previously known to specialize on them, butterfly and moth experts had considered them rather uninteresting and ignored them in their research. The discovery of the alpine rose leaf-miner wasn’t the result of a targeted search: it was a pure stroke of luck.

During a cloudy spell in July this year, researchers surveying the butterflies in Ardez in the Engadine valley, Switzerland, happened to take a break exactly at an infested alpine rose bush.

“The accidental sighting of the first caterpillar in an alpine rose leaf was an absolute adrenaline rush, it was immediately clear that this must be an extraordinary species,”
Peter Huemer, researcher and head of the natural sciences department of the Tyrolean State Museums

Peter Huemer, researcher and head of the natural sciences department of the Tyrolean State Museums, and Swiss butterfly and moth expert Jürg Schmid came back in late July and early August to look for caterpillars and pupae and find out more about this curious insect. The extended search yielded evidence of a stable population of a species that was initially a complete enigma.

Life in the leaf

Leaf-mines of the alpine rose leaf-miner moth on *Rhododendron ferrugineum* in Ardez, Graubünden, Switzerland. Photos by Peter Huemer

The alpine rose leaf-miner moth drills through the upper leaf skin and into the leaf interior immediately after the caterpillar hatches. The caterpillar then spends its entire life until pupation between the intact leaf skins, eating the leaf from the inside. Thanks to this behavior, the caterpillar is just as well protected from bad weather as from many predators such as birds, spiders, or some carnivore insects. The feeding trail, called a leaf mine, begins with a long corridor and ends in a large square-like mine section. The feces are deposited inside this mine. When the time comes for pupation, the caterpillar leaves the infested leaf and makes a typical web on the underside or a nearby leaf. With the help of several fine silk threads, it produces an elaborate “hammock”, in which the pupation finally takes place. In the laboratory, after about 10 days, the successful breeding to a moth succeeded, with a striking result.

Enigmatic glacial relic

Final instar larva of the alpine rose leaf-miner moth on *Rhododendron ferrugineum* in Ardez, Graubünden, Switzerland. Photo by Jürg Schmid

Huemer and Schmid were surprised to find out that the moths belonged to a species that was widespread in northern Europe, northern Asia and North America – the swamp porst leaf-miner butterfly Lyonetia ledi. By looking at its morphological features, such as wing color and pattern, and comparing its DNA barcodes to those of northern European specimens, they were able to confirm its identity.

Habitat of the alpine rose leaf-miner moth in Engadine/Switzerland with *Rhododendron ferrugineum*. Photo by Jürg Schmid

The Engadine population, however, is located more than 400 km away from the nearest other known populations, which are on the border of Austria and the Czech Republic. Furthermore, the species lives in northern Europe exclusively on swamp porst and Gagel bush – two shrubs that are typical for raised bogs and absent from the Alps. However, the researchers suggest that in earlier cold phases – some 22,000 years ago – the swamp porst and the alpine rose did share a habitat in perialpine lowland habitats north of the Alps. It is very likely that after the last cold period and the melting of the glaciers, some populations of the species shifted their host preference from the swamp porst to the alpine rose. The separation of the distribution areas of the two plants caused by subsequent warm phases inevitably led to the separation of the moth populations.

Extinction risk

Characteristic cocoon with final instar larva and pupa of the alpine rose leaf-miner moth on *Rhododendron ferrugineum* in Ardez, Graubünden, Switzerland. Photos by Jürg Schmid

The Alpine Rose Leaf-miner Moth is so far only known from the Lower Engadine. It lives in a steep, north-exposed, spruce-larch-pine forest at about 1,800 m above sea level. The high snow coverage in winter and the largely shady conditions in summer mean that alpine roses don’t get to bloom there. The scientists suspect that the moth species can still be discovered in places with similar conditions in the northern Alps, such as in neighboring Tyrol and Vorarlberg. Since the moth is likely nocturnal and flies late in the year, probably hibernating in the adult stage, the search for the caterpillars and pupae is more promising. However, the special microclimate of the Swiss location does not suggest that this species, which has so far been overlooked despite 250 years of research, is widespread. On the contrary, there are legitimate concerns that it could be one of the first victims of climate change.

Research article:

Huemer P, Schmid J (2021) Relict populations of Lyonetia ledi Wocke, 1859 (Lepidoptera, Lyonetiidae) from the Alps indicate postglacial host-plant shift to the famous Alpenrose (Rhododendron ferrugineum L.). Alpine Entomology 5: 101-106. https://doi.org/10.3897/alpento.5.76930

Mosquito populations give a new insight into the role of Caucasus in evolution

We know that the Caucasus is a relatively large mountainous region, situated between Black and the Caspian seas. In its turn, it is divided into three subregions: Ciscaucasia, Greater Caucasus and Transcaucasia, also known as South Caucasus.

A closer look into the chromosome structure of mosquito larvae of a curious group of species (Chironomus “annularius” sensu Strenzke (1959)), collected from the three localities, has allowed Dr Mukhamed Karmokov of the Tembotov Institute of Ecology of Mountain territories at the Russian Academy of Science to figure out how the specificity of the Caucasian region has simultaneously unified its fauna geographically, yet has divided it evolutionarily. His paper is published in the open access journal Comparative Cytogenetics.

Having collected a sufficient amount of mosquito larvae, the researcher managed to study the chromosome structure, rearrangements and possible peculiarities of the separate Caucasian populations, in order to compare them.

Additionally, he analysed their relations to earlier known populations from Europe, Siberia, Kazakhstan and North America.

Amongst the curious peculiarities Karmokov identified in the chromosome structure of the studied larvae were some rearrangements which appear unique to Caucasus. Furthermore, he found that despite the close geographic proximity, the genetic distance between the Caucasian populations is quite significant, even While not enough to determine them as separate species, it could prove them as separate subspecies.

In conclusion, the scientist notes that the obtained data confirm that the Caucasian populations of the studied species have complex genetic structure and provide evidence for microevolution processes in the region.

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Original source:

Karmokov MKh (2018) Karyotype characteristics and chromosomal polymorphism of Chironomus “annularius” sensu Strenzke (1959) (Diptera, Chironomidae) from the Caucasus region. Comparative Cytogenetics 12(3): 267-284. https://doi.org/10.3897/CompCytogen.v12i3.25832

New parasitoid wasp likely uses unique saw-like spines to break out of its host body

About the size of a sesame seed, a new species of wasp from Costa Rica, named Dendrocerus scutellaris, has elaborate branched antennae that could be used for finding mates. Or hosts.

The new insect is described by PhD candidate Carolyn Trietsch, Dr. István Mikó and Dr. Andrew Deans of the Frost Entomological Museum at Penn State, USA, together with Dr. David Notton of the Natural History Museum in London, UK. Their study is published in the open access Biodiversity Data Journal.

The wasp is a parasitoid, meaning that its larvae feed on a live host insect. There are two types of parasitoids: ectoparasitoids, which lay their eggs on or near the host, so that the hatchling larvae can attach to and feed on the insect from the outside; and endoparasitoids, which lay their eggs directly inside the host, so that the larvae can eat them from the inside out.

Unfortunately, to puzzle out the new wasp’s lifestyle, the researchers could only rely on specimens collected back in 1985, which had spent the past few decades stored in the collections of the Natural History Museum of London before being loaned to the Frost Museum at Penn State for research.

What can you learn about a wasp’s lifestyle from specimens that are over 30 years old? Even though the new species has never been observed in the wild, researchers managed to learn a lot by looking at the wasps’ morphology, concluding that the species is likely an endoparasitoid.

The larva of an endoparasitoid wasp needs a safe place to develop and mature, so when it is done feeding on its host, it may stay inside the host’s body where it can develop undisturbed. Once it is fully grown, the adult wasp either chews or pushes its way out, killing the host if it isn’t already dead.

Unlike its close relatives, the new species does not have pointed mandibles for chewing. Instead, it has a series of spines along its back. While the wasp is emerging, it may rub these spines against the host and use them like a saw to cut open the body. Once emerged, it flies off to mate and continue the cycle.

“While their lives may sound gruesome, parasitoid wasps are harmless to humans and can even be helpful,” explain the scientists. “Depending on the host they parasitize, parasitoids can benefit agriculture by controlling pest insects like aphids that damage crops.”

It is currently unknown what the new species feeds upon, but naming the species and bringing it to attention is the first step in learning more about it.

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Original source:

Trietsch C, Mikó I, Notton D, Deans A (2018) Unique extrication structure in a new megaspilid, Dendrocerus scutellaris Trietsch & Mikó (Hymenoptera: Megaspilidae). Biodiversity Data Journal 6: e22676. https://doi.org/10.3897/BDJ.6.e22676

Flying jewels spell death for tarantulas: Study of a North American spider fly genus

Spider flies are usually a rarely encountered group of insects, except in Western North America, where the North American jewelled spider flies (the Eulonchus genus) can be locally abundant in mountainous areas such as the Sierra Nevada of California. The brilliantly coloured adults (also known as ‘sapphires’ and ’emeralds’) are important pollinators of flowers.

The North American jewelled spider flies typically have large rounded bodies covered with dense hairs and metallic green to blue or even purple colouration, giving them a jewel-like appearance. Together, the elongated mouthparts, the metallic coloration and the eyes, covered with soft hairs, immediately set these flies apart from any other group of tarantula fly. The mouthparts are greatly elongated to help them feed on nectar from the flowers of more than 25 different plant families and 80 species.

However, their larvae are more insidious, seeking out and inserting themselves into tarantula hosts and slowly eating away their insides until they mature and burst out of the abdomen, killing the spider, and leaving behind only the skin. Once they have emerged from the host, they pupate to develop into adults.

In the present study, published in the open access journal ZooKeys, six species of the genus are recognized in North America, including one from the Smokey Mountains, and five from the West, ranging from Mexico to Canada. Drs Christopher J. Borkent and Shaun L. Winterton, and PhD student Jessica P. Gillung, all affiliated with the California State Collection of Arthropods, USA, have redescribed all of them using cybertaxonomic methods of natural language description. A phylogenetic tree of the relationships among the species is also presented.

The examined individuals include many from the collection amassed by the late Dr. Evert Schlinger (1928-2014) over the span of more than 60 years. Today, the collection resides at the California Academy of Sciences (CAS). “Dr. Evert I. Sclinger was a world renowned expert on spider fly taxonomy and biology,” write the authors in the paper, which they dedicate to the scientist and his legacy.

All of the studied flies are relatively widely distributed, and locally abundant, except for a single species (E. marialiciae), which is known from only a few specimens, collected within a small contiguous area in the Great Smoky Mountains. However, the scientists suggest that future studies are needed to explore whether this is actually their full range.

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Original source:

Borkent CJ, Gillung JP, Winterton SL (2016) Jewelled spider flies of North America: a revision and phylogeny of Eulonchus Gerstaecker (Diptera, Acroceridae). ZooKeys 619: 103-146. doi: 10.3897/zookeys.619.8249