Some interesting facts from the world of insects

Clay Bumblebees (Bombus argillaceus) stand out among bumblebees owing to their queen differing from the workers not only in colour, but also in size. Whereas workers and males have a yellow band and a white tip on their abdomen, the queen’s abdomen is completely black. The species was described by I. A. Scopoli on the basis of specimens from Slovenia. In the Karst, Clay Bumblebees have always been among the commonest bumblebees.

Elsewhere in Slovenia, the Clay Bumblebee is among the rarest, since this is a thermophilous Mediterranean species. We badly missed Clay Bumblebees in 2016, as they disappeared almost in the entire country. I, personally, recorded only two queens in the Karst and at the source of the Krka River, both with a white tip on the abdomen, which is a typical feature of the female workers. They were also smaller in size than the characteristic queen with the black abdomen, which can exceed 2 cm in size. The smaller size is most probably due to the lack of food during the summer when these bumblebees rear a new generation of sexual individuals. Food shortage as a result of unfavourable weather conditions or human-caused environmental changes is one of the most significant causes of the disappearance of wild bees of already catastrophic proportions.

During the summer, Ljubljana reminds us with its soundscape of a Mediterranean seaside town. In the blue sky, we can see and hear squawking Yellow-legged Gulls (Larus michahellis), which otherwise nest on the buildings’ flat roofs covered by gravel,  while in the city parks the high-pitched buzzing by Ash Cicadas (Cicada orni) can be heard..

Adult Ash Cicadas live for a little less than two weeks, with the males tirelessly and incessantly singing to attract females. Fertilized females lay their eggs in herbaceous plants and the hatched larvae fall to the ground and dig themselves in the soil, where they suck juices from roots. After two to three years of underground development, adult cicadas hatch again in July.

Ash Cicadas probably came to Ljubljana more than a decade ago with a railway cargo, considering that we listened to the first one at Vojkova Street next to the freight terminal of the Ljubljana Railway Station. Since then, their population has been increasing year by year, and decreased only during truly severe winters, when the ground freezes deeply and kills their larvae. 

Listen how it sings!

Dalmatian Purplescent Beetle (Purpuricenus dalmatinus) is a beetle of the Cerambycidae family. It is distributed from southwestern Slovenia to the Aegean Sea. In Slovenia, it was recorded only in the Vipava Valley, and nowadays only two 100-year-old specimens from Bianchi’s collection remind us of the former population of this species.

Anton Karl Vincenc Bianchi (1858-1933), an employee of the then Ajdovščina Savings Bank, carried out in the 19th century a major research into the Vipava Valley beetles. Bianchi’s beetle collection is an extremely valuable document of the former Vipava Valley beetle fauna.

The collection most probably came to the Slovenian Museum of Natural History Museum in 1946. By stored in large two-part boxes with peat as a base, it was not safe from pests. The curator at the time, Alfonz Gspan, thus decided to transfer the specimens to other beetle collections (Stussiner’s and Staudacher’s and his own, which already belonged to the Museum at the time,). After 1982, Savo Brelih founded the so-called Central Collection of Slovenian Beetles and re-mounted as well as identified all Bianchi’s beetles collected in the territory of Slovenia and stored them in this collection.

The discovery of the first cave beetle was of special significance for the history of Slovenian entomology and natural history. It was also the first described cave insect in the world. Until then, it had not been known that insects could even live in caves.

In 1831, the species was found in the Postojna Cave by Luka Čeč, the Cave’s assistant lamplighter. He passed it on to Count Franz Hohenwart, who in turn entrusted it to Ferdinand J. Schmidt for expert identification. In 1832, Schmidt described it in the magazine Illyrisches Blatt as a new genus and a new species – Leptodirus hochenwartii.

As the first specimen of this cave beetle was damaged, Schmidt promised 25 golden coins to the finder of a new specimen. The attractive reward, however, was never paid. The second specimen was found 16 years later on the same spot by Schmidt himself. When searching for the rare beetle, Schmidt came across a whole series of unknown cave animals in the Postojna Cave and some of its neighbouring caves as well. The unexpected finds aroused great interest around the globe and attracted many foreign researchers to visit Carniola. A new discipline in biology began, later named speleobiology.

The Deer Fly (Lipoptena cervi) is also known as Deer Louse or Deer Ked. The latter name, however, is not well-chosen, as it is not classified in the order of animal lice (Phthiraptera), but sooner in the order of Diptera, in the family of Louse Flies (Hippoboscidae).

The Deer Fly is an external parasite on red deer and roe deer, on which both males and females suck blood. Feedings last 15-25 minutes each, and after each of them, the larva begins to develop in the female. These parasites reproduce by adenotrophic vivipary. Specifically, the larva completes its entire development in three stages in the uterine tube of the female, where it feeds on glandular secretions. The nutrient secretions are partially stored in the digestive tract and consumed only during the metamorphosis into pupa. Larvae are deposited just before pupation. In a very short time, the larva transforms into a barrel-shaped pupa, called puparion, which gradually turns black. The puparion is oval-shaped and falls from the host to the leaf litter on the ground. Then it turns into an adult winged fly that circles around in search of a host for its first meal of blood, attracted by the warmth and smell of skin secretions. When it finds one, the wings break off to prevent it from moving through the fur, and remains attached to the same host for the rest of its life.

In the Collection of External Parasites of the Slovenian Museum of Natural History one can see that the main hosts are red deer and roe deer. Particularly in the autumn, a Deer Fly often lands on humans and other mammals and birds. As its wings immediately break off upon thermal stimulus, it is too late when it realizes that the host is not the right one. It is even more fatal when it accidentally lands on the warm bonnet of a car, which is also documented in this collection. 

The Ant Mimic Jumping Spider (Myrmarachne formicaria) measures up to 6 mm in size and is a true master of mimicry. With its brown-black colour of the body, it gives the impression of a segmented body like in ants. With its first pair of legs it flickers like ants with their feelers. Males are equipped with highly elongated chelicerae on the front part of the body, which constitute no less than half the length of the cephalothorax. Such mimicry helps them catching their prey, i.e. ants.

We were highly surprised when we unwrapped a small chocolate bar and three oblong, flat bugs about 3 mm in size jumped instantaneously out of it. The traces of their feeding were found only in the chocolate coating, but not in the white filling. These were Saw Toothed Grain Beetles (Oryzaephilus surinamensis), which are among the commonest pests on stored grain, where they bore into the grain and feed on sprouts. By doing so, they reduce seed germination. Adults do not fly, so humans are solely responsible for their spread throughout the globe.

Cerambyx welensii belongs to the family Cerambycidae. It is distributed in the Northern Mediterranean countries, from the Iberian Peninsula and southwestern France to the Black and Aegean Seas. In the north, it reaches Hungary and Slovakia. In Asia, it can be found in southern Turkey, Lebanon, Israel and Jordan. In Slovenia, it was registered only in the Vipava Valley, so presently we are only reminded of this population thanks to the more than 100-year-old specimens housed in the Slovenian Museum of Natural History.

Anton Karl Vincenc Bianchi (1858-1933), an employee of the then Ajdovščina Savings Bank, carried out in the 19th century a major research into the Vipava Valley beetles. Bianchi’s beetle collection is an extremely valuable document of the former Vipava Valley beetle fauna, bearing witness to the environmental change in the previous century.

The collection most probably reached the Slovenian Museum of Natural History Museum in 1946. By being stored in large two-part boxes with peat as a base, it was not safe from pests. The curator at the time, Alfonz Gspan, thus decided to include the specimens in other beetle collections (Stussiner’s and Staudacher’s and his own, which already belonged to the Museum at the time). After 1982, Savo Brelih established the so-called Central Collection of Slovenian Beetles and re-mounted as well as identified all Bianchi’s beetles collected in the territory of Slovenia and stored them in this collection.

Owing to their characteristic glistering structural colours, from blue and green to red, copper and gold, Cuckoo Wasps (Chrysididae) are amongst the most attractive insects of the Hymenoptera order. The colour effects are created by the reflection and interference of light on the insects’ multi-layered chitinous skeleton. Their larvae are mostly parasites in the nests of other stinging Hymenoptera. Cuckoo Wasps are most often recorded in places where their hosts make their nests. This can be old dead wood or soil with the host species’ nesting burrows. The populations of Cuckoo Wasps depend on the abundance and stability of the populations of their hosts which, however, have been swiftly disappearing from our nature in the last few decades. Specifically, there are fewer and fewer blooming meadows that are either overgrown with forest, intensively cultivated or urbanized. As a consequence, wasps and bees are losing food sources and, at the same time, it is also more difficult for them to find suitable nesting places. Museum collections are valuable sources of information on the disappearing fauna.

During the winter months, mosquitoes do not bite us and we do not see them in nature or in our home environment. Hence, where do mosquitoes hide in the winter or how do they hibernate? Some species overwinter as adults in animal burrows, caves, rock crevices, etc., as well as in human buildings such as basements and attics, stables, outbuildings, greenhouses, garden sheds, etc. Other species hibernate in our climate as eggs laid by the females close to water bodies in autumn and wait for favourable spring temperatures and the first heavy spring rains to hatch as a new generation of larvae. Mosquitoes are insects with complete transformation. Females lay their eggs on the margin of water surfaces or in the water itself. Larvae develop from them, and after three moults the adult larvae pupate. Adult mosquitoes, both males and females, hatch from pupae on the surface of the water. In Slovenia, we have recorded 37 species of mosquitoes so far.

For more photos, see the Invertebrate Photo Database.

The Oriental Hornet (Vespa orientalis) is native to the eastern Mediterranean, southwestern Asia and northeastern Africa. This species constructs its nest of paper-like material in underground cavities or in hollows above the ground. In 2018, an active nest of the Oriental Hornet was found for the first time not far from us, in a wall close to the Port of Trieste. It was probably unintentionally carried there by maritime transport. It has clearly adapted to the urban environment, which has facilitated its survival a great deal further north from its natural range. In 2019, the species was already widespread in the city. Hence, it was not surprising that it was soon discovered in Slovenia as well. In September 2019, a beekeeper Dragan Stupar found the first individual in our territory at his beehives in Ankaran. At the instigation of the National Veterinary Institute and the National Institute of Biology, the species is now part of the Hymenoptera collection in the Slovenian Museum of Natural History.

During a walk along the Koseški bajer, I came across a colourful marble with a striped brick-yellow pattern. As soon as I picked it up, I realized that it was not made of glass and, even more strangely, that it was accreted to a dry oak leaf.

Such formations on different parts of plants are called galls. They are formed by representatives of various animal groups, which secrete substances similar to plant hormones that cause directional growth of plant tissue. They serve as shelter and food for developing larvae and pupae. In this case, I was dealing with a gall wasp (Hymenoptera: Cynipidae) that acquired the Slovenian name Striped Pea Gall (Cynips longiventris) after the pattern on the gall. The latter contains a larva that completes its development and will pupate and hatch as an adult insect in spring.

More about its very complex development with the alternation of sexual and asexual generations and their galls and even more pictorial material can be found in the Invertebrate Photo Database.