Insects

Thysanura (Zygentoma)

Thysanura or Zygentoma are small to middle-sized wingless insects (5 – 30 mm long) that have elongated, slightly flattened bodies with three subequally long tail-like filaments extending from their last segment.

They move by wiggling their bodies. All species are fast runners, but unlike Archaeognatha, they cannot jump. Thysanuras have external fertilization. They live in caves and in the soil (some species are commensals in ant nests), while some, like the most common species Lepisma saccharina (silverfish), can be found in human houses. They inhabit humid microhabitats inside of the house and can be found in sinks or bathtubs because they have difficulty moving on smooth surfaces. They feed on decomposing organic matter.

Zygentoma comprise of around 370 species in about 90 genera and five families (Lepismatidae, Nicoletiidae, Ateluridae, Lepidothrichidae i Maindronidae) widespread around the world.

Only the family Nicoletiidae has their representatives in subterranean habitats, which are either troglobionts or guanobionts. Out of some 80 species of this family, about 20% are limited to life in caves. Subterranean species are known from few localities in the Mediterranean and in the tropical areas, and include some of the highly troglomorphic forms.

Trorepnjak

It is important to mention the genus Coletinia Wygodzinsky, 1980. This genus includes 21 known species of which most are from Mediterranean area, mainly from Iberian Peninsula where the most research on this genus has been done. They are found in underground, mostly caves, while some are adapted to life in edaphic environments. This group is poorly researched in Croatia, and the only recorded species is C. maggi (Grassi, 1887), found in the valley of river Ombla near Dubrovnik city. Members of this genus have also been found in northern Adriatic region, Istria and Kvarner respectively, but they were only juvenile specimens without developed determination characters . To determine the species level, sexually mature male is needed.

As a result of increasing interest in biospeleology, growing knowledge about this group as well as its associated species is noticeable, and new discoveries about their biology and ecology are emerging.

BIBLIOGRAPHY:

  • Gilgado, J. D. & Ortuño, V. M. (2015): Intra- and inter-population polymorphism in Coletinia maggii (Grassi, 1887) (Zygentoma: Nicoletiidae), an inhabitant of soil, mesovoid shallow substratum (MSS) and caves–A challenge for the strict classification of subterranean fauna?. Zootaxa 3920(1): 85-100.
  • Gunn, J. (2004): Encyclopedia of Caves and Karst Science. Taylor & Francis, New York. pp. 964.
  • Habdija, I., Primc-Habdija, B., Radanović, I., Špoljar, M., Matoničkin-Kepčija, R., Vujčić-Karlo, S., Miliša, M., Ostojić, A. & Sertić-Perić, M. (2011): Protista – Protozoa Metazoa – Invertebrata – strukture i funkcije. Alfa, Zagreb: 427-428.
  • Resh, V. H. & Cardé, R. T. (2009): Encyclopedia of Insects. Second Edition. Academic Press. 1070-1071.
  • Wygodzinsky, P. (1980): A Survey of the Nicoletiinae of Europe (Nicoletiidae, Thysanura, Insecta). American Museum Novitates 2695: 1-24.

Orthopteran (Orthoptera)

The orthopteran (Orthoptera), more precisely the family Rhaphidophoridae, are found in large numbers on the walls of cave entrances. They are troglophilic, and use caves to spend the winter and avoid the summer heat. They find their way in the dark with the help of long antennae, and avoid predators by jumping with powerful hind legs. Rhaphidophoridae family members are omnivore, meaning they feed on both plant and animal food.

In Croatia, there are 5 species that inhabit caves. Dolichopoda araneiformis is endemic of the western Mediterranean. It is spread from the city of Dubrovnik to Greece, and is described from a cave in the vicinity of the city of Dubrovnik. Within the genus Troglophilus, there are three species in Croatia. T. cavicola lives in continental Croatia and Istria, T. brevicauda is known from Žumberak and Kordun region, and T. neglectus lives in the entire territory of Croatia and is described from the cave in the Istria region. In the Mediterranean lives Gryllomorpha dalmatina whose larvas are commonly found in caves during the winter, while adults are rare. Although troglophilic orthopterans are not fully adapted to cave habitats, their populations have been observed in pits at depths greater than 150 m.

BIBLIOGRAPHY:

  • Di Russo, C., Rampini, M., Latella, L. & Cobolli, M. (2014): Measurements of the diet in two species of Troglophilus Krauss, 1879 cave crickets from Italian subterranean habitats (Orthoptera, Rhaphidophoridae). Subterranean Biology 13: 45-54. https://doi.org/10.3897/subtbiol.13.6719
  • Gottstein Matočec, S. (ed.), Bakran-Petricioli, T., Bedek, J., Bukovec, D., Buzjak, S., Franičević, M., Jalžić, B., Kerovec, M., Kletečki, E., Kralj, J., Kružić, P., Kučinić, M., Kuhta, M., Matočec, N., Ozimec, R., Rađa, T., Štamol, V., Ternjej, I. & Tvrtković, N. (2002): An overview of the cave and interstitial biota of Croatia. Nat. Croat., Vol. 11, Suppl. 1: 1-112.

Beetles (Coleoptera)

Beetles (Coleoptera) are the largest order of the class of insects (Insecta). So far, about 360,000 species have been described in the world, forming 211 families.

The families which can be often found in subterranean habitats of Dinarides are:

  • ground beetles (Carabidae)
  • cholevid beetles (Cholevidae = Leiodidae)
  • rove beetles (Staphylinidae)
  • weevils (Curculionidae)

A large number of troglobiont species in the Dinarides and the eastern part of Southern Calcareous Alps belong to the family Carabidae (142 species) and Cholevidae (246 species). This means that, in the mentioned area, cholevid beetles (Cholevidae) include more than twice as many species as the ground beetles (Carabidae). The third most common family in subterranean habitats is rove beetles (Staphylinidae), with 45 troglobiotic species recorded in the Dinarides. In Croatia, more than 140 species from the four most numerous families in subterranean habitats have been recorded.

Considering the number of species, fauna of cholevid beetles (Cholevidae) of the Balkan Peninsula is the richest in the world. This positions Croatia among countries with the greatest biodiversity of subterranean beetles on the global level. The cholevid beetles live on all continents (excluding Antarctica) and are represented by species size from 0.8 to 9 mm. They can be saprophagous (feeding on decaying matter), necrophagous (feed on dead or decaying animal flesh), guanophilous (feeding on excrement of bats), and are usually hygrophilous (living in moist places) and light-avoiding.

Within the family of cholevid beetles, the subfamily Leptodirinae contains the highest number of species. It is distributed, with few exceptions, in the Western – Palaeartic Region. It includes the most troglobiotic species – subterranean beetles that are the most adapted to cave conditions, species of genera Leptodirus and Graciliella. It also includes higropetric species of genera Radziella, Croatodirus, Velebitodromus that live in a similar biotope called “cave higropetrik”, where continuous thin film of water flows over walls. The three mentioned genera are characterized by special mouthparts, which are probably used to filter nutrients from water.

Other species of this subfamily are also characterized by high endemic rate in Croatia.

Endemic genera for Croatia are Anisoscapha, Croatodirus, Dalmatiola, Hoffmannella, Radziella, Redensekia, Roubaliella, Zariquieyella, Spelaeobates, Spelaites, Speoplanes and Velebitodromus.

Narrow-necked cave beetle (Leptodirus hochenwartii Schmidt, 1832) was the first described troglobiotic invertebrate in the world. This species is on the list of target species of ecological network Natura 2000, which is why it is very important in conservation of subterranean fauna and habitat. There is one species of the genus Leptodirus and six subspecies, four of which live in Croatia. Leptodirus hochenwarii reticulatus Müller, 1904, was described from the cave Grotta Noe near Trieste in Italy. In Croatia, it lives in the north of Ćićarija Mt., which is the southern border of the areal of this subspecies. Leptodirus hochenwartii pretneri Müller, 1926 is described from the cave Jama nad Zasten near Mune on Ćićarija Mt. It is widespread on Ćićarija Mt. and partly on Učka Mt., and is endemic to Croatia. Leptodirus hochenwartii croaticus Pretner, 1955 is described from the cave Ledena špilja kod Lokava. It lives in caves in Gorski Kotar and part of Lika, near northern slopes of Velebit Mt. It is endemic to Croatia. Leptodirus hochenwartii velebiticus Pretner, 1970 is described from the cave Vrtlina jama on the southern Velebit Mt. It is widespread in the southern part of Velebit Mt., which is also the southern edge of the areal of the species; it is also endemic to Croatia.

Narrow-necked cave beetle is a true troglobiotic beetle, without eyes or pigment. It varies from 8 to 11 mm in size. It has a thin pronotum, “inflated” abdomen and extremely elongated body appendages. Ecology and ethology of this species are poorly known because studies have never been systematically implemented. It is a detrivor and feeds off a variety of organic remains. It displays a typical “K reproductive strategy”, has a reduced number of developmental stages, and deposits a small number of large eggs. Larvae are hatched large and do not feed but immediately enter the pupa stage and transform to the imago.

The second most numerous family in the subterranean habitats are ground beetles (Carabidae), from which most species belong to subfamily Trechinae. Ground beetles are on top of the food web of invertebrates in cave habitats because they are mostly predators. The largest predators are the species of the genus Laemostenus, with size up to 22 mm. Endemic genera for Croatia are Biokovoaphaenopsis, Croatotrechus, Derosiella, Jalzicaphaenops, Lovricia and Neolovricia.

The third most numerous family in subterrenean habitats are rove beetles (Staphylinidae). Most species from this family belong to subfamily Pselaphinae, and a smaller number to subfamily Scydmaeninae. Staphylinidae are one of the largest family of beetles in the world, but among them only about one hundred species have successfully adapted to subterranean habitats. Endemic genera for Croatia are Biokovobythus, Melledobythus, Pauperobythus and Velebythus.

Numerous species of subterranean beetles new to science are being described every year in Croatia, with many ongoing studies on this group.

CONTACT:
Branko Jalžić – jalzicbranko@gmail.com
Petra Bregović – bregovicpetra@gmail.com

BIBLIOGRAPHY

  • Bouchard, P., Bousquet, Y., Davies, A. E., Alonso-Zarazaga, M. A., Lawrence, J. F., Lyal, C. H. C., Newton, A. F., Reid, C. A. M., Schmitt, M., Ślipiński, S. A. & Smith, A. B. T. (2011): Family-group names in Coleoptera (Insecta). ZooKeys 88: 1-972.
  • Bouchard, P., Grebennikov, V. V., Smith, A. B. T. & Douglas, H. (2009) Biodiversity of Coleoptera. In: Foottit, R. G. & Adler P. H. (eds): Insect biodiversity: science and society. Blackwell Publishing, Oxford. pp. 656: 265–301.
  • Bregović, P. & Jalžić, B. (in prep.): Coleoptera. In: Encyclopedia biospeologica, second edition.
  • Bregović, P. & Zagmajster, M. (2016): Understanding hotspots within a global hotspot – identifying the drivers of regional species richness patterns in terrestrial subterranean habitats. Insects Conservation and Diversity 9: 268-281.
  • Casale, A., Grafitti, G. & Latella, L. (2009): The Cholevidae (Coleoptera) of Sardinia. Zootaxa 2318: 290-316.
  • Dražina, T., Čuković, T., Bregović, P. & Jalžić, B. (2015): Zaštitom tankovratića (Leptodirus hochenwartii Schmidt, 1832) do zaštite podzemlja. Subterranea Croatica 18: 38-44.
  • Hlaváč, P., Nakládal, O. & Jalžić, B. (2014): Endogean and cavernicolous Coleoptera of the Balkans. XIV. Melledobythus bilandzijae, new genus and species of cavernicolous Bythinini (Staphylinidae: Pselaphinae) from the Island Mljet, Croatia. Zootaxa 3835: 564-572.
  • Hlaváč, P., Ozimec, R. & Pavićević, D. (2008): Catalogue of the troglobitic Pselaphinae (Coleoptera, Staphylinidae) of the Balkan Peninsula, with a key to genera. In: D. Pavićević & M. Perreau (eds), Advances in the studies of the subterranean and epigean fauna of the Balkan Peninsula, Papers dedicated to the memory of Guido Nonveiller. Institute for Nature Conservation of Serbia, Belgrade, Monographs, 22. pp. 564: 307-328.
  • Jalžić, B. (2002): Coleoptera. In: Gottstein Matočec, S. (ed.), Bakran-Petricioli, T., Bedek, J., Bukovec, D., Buzjak, S., Franičević, M., Jalžić, B., Kerovec, M., Kletečki, E., Kralj, J., Kružić, P., Kučinić, M., Kuhta, M., Matočec, N., Ozimec, R., Rađa, T., Štamol, V., Ternjej, I. & Tvrtković, N. (2002): An overview of the cave and interstitial biota of Croatia. Nat. Croat., Vol. 11, Suppl. 1: 1-112: pp. 69-74.
  • Njunjić, I., Perreau, M., Hendriks, K., Schilthuizen, M. & Deharveng, L. (2016): The cave beetle genus Anthroherpon is polyphyletic; molecular phylogenetics and description of Graciliella n. gen. (Leiodidae, Leptodirini). Contributions to Zoology, 85, 3: 337-359.

Caddisfly (Trichoptera)

The caddisflies (Trichoptera) are holometabolous insects closely related to moths (Lepidoptera). Life cycle (holometaboly) with complete metamorphosis means developing different morphology and habitats through four life stages: eggs, larvae, pupae and adult (imago). First three stages develop in the aquatic ecosystem, while imago inhabits terrestrial ecosystem. In the larval stage, caddisfly have different feeding types (detrivores, herbivores, carnivores) characteristic for the family, and even for the species. Imago has specific mouth organ for feeding on liquids (e.g. flower nectar). Most of the caddisfly larvae construct various types of portable cases, often incorporating sand and small pebbles, or bits of leaves and twigs, and each genus or even species builds its own particular style of case.

The caddisfly fauna is represented with a small number of troglophile species in subterranean habitats. So far, 10 caddisfly species have been discovered (Stenophylax vibex Curtis 1834; S. permistus McLachlan, 1895; S. mucronatus McLachlan, 1880; Micropterna testacea (Gmelin, 1789); M. sequax McLachlan, 1875; M. nycterobia McLachlan, 1875; M. lateralis (Stephens, 1873); M. wageneri Malicky, 1971; Wormaldia occipitalis (Pictet,1834); W. subnigra McLachlan, 1865),which belong to two families (Limnephilidae and Philopotamidae). This group of insect is poorly investigated in subterranean habitats, mainly because most of the studies are focused on surface waters of aquatic ecosystem where they represent valuable bioindicators, as they are sensitive to water pollution.

Adult caddisflies use caves for summer diapause (aestivation), and mating has also been observed. Larvae drift into caves on temporal water flows, and find  a shelter from predators. The time spent in cave depends on species, but geographical latitude and longitude also have a role in it (with increasing latitude, time spent in subterranean habitats decreases).

BIBLIOGRAPHY

  • Gottstein Matočec, S. (ed.), Bakran-Petricioli, T., Bedek, J., Bukovec, D., Buzjak, S., Franičević, M., Jalžić, B., Kerovec, M., Kletečki, E., Kralj, J., Kružić, P., Kučinić, M., Kuhta, M., Matočec, N., Ozimec, R., Rađa, T., Štamol, V., Ternjej, I. & Tvrtković, N. (2002): An overview of the cave and interstitial biota of Croatia. Nat. Croat., Vol. 11, Suppl. 1: 1-112.
  • Holzenthal, R. W., Blahnik, R. J., Prather, A. L. & Kjer, K. M. (2007): Order Trichoptera Kirby, 1813 (Insecta), Caddisflies. Zootaxa, 1668: 639-698.
  • Kučinić, M., Ćukušić, A., Žalac, S., Podnar, M., Kambarovich Akhmetov, K., Akimbekova, N., Moldazhanovna Zhumadina, S. & Vučković, I. (2017): First DNA barcoding and new records of the Mediterranean caddisfly species Micropterna wageneri Mal. (Trichoptera, Limnephilidae) in Croatia with note on DNA barcoding and diversity of genus Micropterna in Croatia. Nat. Croat., Vol. 26, No. 1, 81–98, Zagreb
  • Salavert, V., Zamora-Muñoz, C. & Tinaut, A. (2011): Distribución de tricópteros troglófilos (Trichoptera: Limnephilidae) en cuevas andaluzas (Andalucía, España). Boletín de la Asociación española de Entomología, 35(3-4): 325-344.
  • Waters, T. F. (1981): Drift of stream invertebrates below a cave source. Hydrobiologia, 78 (2): 169-175.

Butterflies (Lepidoptera)

Butterflies (Lepidoptera) use caves during unfavorable winter conditions or to feed on roots. For Croatian fauna, 11 troglophilic species are recorded.

The species that most commonly inhabit caves in Croatia are Triphosa dubitata and Scoliopteryx libatrix, which can be present in caves up to 150 m deep. One interesting finding was more than 1,000 observed specimens of T. doubitata in cave Vrelo in Gorski Kotar region.

BIBLIOGRAPHY:

  • Gottstein Matočec, S. (ed.), Bakran-Petricioli, T., Bedek, J., Bukovec, D., Buzjak, S., Franičević, M., Jalžić, B., Kerovec, M., Kletečki, E., Kralj, J., Kružić, P., Kučinić, M., Kuhta, M., Matočec, N., Ozimec, R., Rađa, T., Štamol, V., Ternjej, I. & Tvrtković, N. (2002): An overview of the cave and interstitial biota of Croatia. Nat. Croat., Vol. 11, Suppl. 1: 1-112.

Diptera (Diptera)

Due to constant darkens in the underground, one of the typical adaptations to cave life among insects is wing reduction. So far, the only known exception to this rule is a dipteran of the family Chironomidae named cave hajdi (Troglocladius hajdi Andersen, Baranov & Hagenlund, 2016), scientifically described in 2016.

Cave hajdi is known from one cave only, Lukina jama- Trojama on Velebit Mt in Croatia. Next to typical troglomorphic adaptations like depigmentation, reduction of visual apparatus and elongation of body appendages, this species is extraordinary for retaining big and probably functional wings. Although researchers did not observe it flying, she can at least use its wings for soaring small distances.

DNA analyses confirmed morphological inference and revealed that not only is the species new to science, but that it also belongs to a new genus, and that it is genetically distant from other members of the family. A habitat in which cave hajdi is found also confirms its uniqueness – deep parts of Lukina jama pit, below 800 m of depth, indicate its isolation. So far, only adult females were found, which means that it is possible that the species is parthenogenic and that no males exist. The larvae are probably living in the water and an effort should be made to collect them during future expeditions.

BIBLIOGRAPHY:

Planthoppers (Hemiptera)

Cixiidae are a family of insects (Insecta) whoose looks resemble miniature cicadas (Cicadidae family). They are members of a group called Fulgoromorpha or planthoppers, a name that describes typical adult behavior – plant hopping. Adults can be found on the surface of plants while nymphs commonly live at the base of plants on the surface, or between the roots where they feed.

In Croatia 35 species can be found from the family Cixiidae, of which one is entirely troglomorphic. The species name is Trirhacus helenae, and it can be found on the island of Mljet. It is one of two Mediterranean troglomorphic species with typical traits as lack of pigment, eye reduction and a complete life cycle underground.

Cixiidae are a valuable group for studying evolution mechanisms that led to the subterranean life. Best example for this is genera Oliarus with its few species living on the Hawaiian Islands. These species can have populations adapted for life on surface, in half-dark conditions or in the subterranean habitat. This is an example of gradual adaptation, one of few hypotheses how animals populated the underground habitats. It is assumed that the diversification of habitat choice is a result of the nymph stage living underground. Gradually, the nymph stage ventured deeper underground in search for food and after some time the adult stage stayed underground instead of returning to the surface.

BIBLIOGRAPHY:

  • Hoch, H. (1999): The Hawaiian cave planthoppers (Homoptera: Fulgoroidea: Cixiidae) – a model for rapid speciation?. International Journal of Speleology, 26 (1–2): 21-31.
  • Hoch, H. (2013): Trirhacus helenae sp. n., a new cave-dwelling planthopper from Croatia (Hemiptera: Fulgoromorpha: Cixiidae). Mitteilungen Aus Dem Museum Fur Naturkunde in Berlin – Deutsche Entomologische Zeitschrift, 60 (2): 155-161. https://doi.org/10.1002/mmnd.201300021
  • http://bioteaching.com/cixiidae-hemiptera-fulgoromorpha/ posjećeno: 22.5.2017.
  • http://insectoid.info/checklist/cixiidae/croatia/ posjećeno: 22.5.2017.