Lyristes plebejus Scolopi, syn.: Tibicen plebejus (Scopoli), Cicada plebeja ScollopiFamily: CicadidaeOrder: HemipteraEN: Common Cicada, DE: Gemeine Singzikade, Grosse ZikadeSlo.: veliki kratDat.: June 22. 2015 Lat.: 44.76598 Long.: 14.76588Code: Bot_891/2015_ DSC7432 Habitat: a small lot of dry unmaintained grassland surrounded by a house, a road and bushes; flat terrain; open, sunny, dry place; Eocene clastic sediment ground; average precipitations ~ 900 mm/year, average temperature 13-14 deg C, elevation 75 m (250 feet), Mediterranean phytogeographical region. Place: Adriatic Sea region, island Rab, next to the road from town Rab to settlement Mundanije direction village Supetarska draga, Zadar archipelago, Zadar region, Croatia. Comment: Lyristes plebejus is only one among more than 1.000 species in the insect family Cicadidae (cicadas). It is essentially a Mediterranean species and one of the largest in Europe measuring up to 4 cm in length and up to 10 cm across the wings. However, it can be found also extending north to central Europe and east to Armenia, Georgia and Iran.Cicadas are in many aspects extraordinary creatures. They are best known by emitting shrill sound, sometimes in large choruses of hundreds insects, which can be heard all day when the weather is hot enough in open woods, olive groves and garrigue all along the shores of Mediterranean Sea. Millions of tourists visiting Mediterranean countries in summer know well their song (called cymbalization) but not many have really seen the creature, which produce it. Because of their very mimetic appearance (see Fig. 3) and their ability to stop their singing as soon as you approach them, it is quite challenging to spot them or photograph them from close in the wild. Only male insects produce cymbalization to allure females for copulation. The sound is produced through vibration of a paired membrane at the base of their abdomen. The high pitch sound is astonishing laud - at the source in some species more than 100 dB! Each species in the genus has its own specific song. It enables scientists to detect a presence of many species in a habitat without seeing and collecting them, just by recording and analyzing their acoustic emissions.The Lyristes plebejus has five eyes! Two are compound eyes (common with most insects) consisting of hundreds of individual eye cells each. Three, vividly red one, and centrally positioned in front of the head in triangular pattern (see Fig. 4), are spot eyes. Exact function of them is still not understood completely. It seems that they enable the animal to better see 3D-wise. Namely, since both side compound eyes only have a limited common view-field (which is a prerequisite for a stereo picture), they are limited in the respect of three dimensional eyesight. The species is a very fast flying insect, also through bushes and canopies of dense Mediterranean vegetation without ever touching unintentionally a single branch or twig. 'Technically' this must be a really hard navigational problem, which appears mother nature resolved it by these five eyes.The phenology (life cycle) of the Lyristes plebejus is also very interesting. Eggs are laid behind bark of bushes and trees. When small, white larvae appear they fall to ground and drill themselves underground where they feed from the sap of roots. They stay there for many years. Usually Lyristes plebejus lives underground for five years as a nymph, some species from America stay underground for 17 years! They molt their exoskeletons several times to allow growth until they reach their final nymph size, which is approximately the same size as adult insects. Most surprising fact is that they all crawl out of the ground into the open almost at the same time. What powers their 'internal clock' all these years in the dark is unknown. In a small lot of dry unmaintained grassland of about 10 x 10 m, where I observed their hatching into adult insects in 2015 (Fig. 7 click picture twice!), they appeared massively, all of them within two days. There were more than a hundred of empty skeletons lying on ground after the second day (Fig. 6). Their life as a mature, free flying insects is short, indeed, very short compared to their underground existence as a nymph only about two months.There are two facts, which particularly amazed me during approximately two-hour hatching process from their appearing out of the ground to flying away as a completely functional grown-up individual: their motionlessness during the process and their sudden flyoff.After appearing out of the ground in less than five minutes the nymph finds an appropriate grass stalk or similar elevated support and climbs it. It takes a horizontal hanging position or even turns head-down and settles down completely motionless. During the whole process of hatching its body remains totally passive (with just two exceptions described ahead). After its skeleton cracks along upper side near the head (Fig. 7- at 9:37) the greenish, soft new body starts slowly to come out. It looks like some miraculous power gradually quizzes it out of its dead but complex skeleton (Fig. 5). The process looks like a very slow squeezing of tooth paste out of a tube (Fig. 7 - from 9:39 to 9:47). The body itself remains completely passive. Not a single minute motion of a limb, tentacles, head or abdomen as a help to free itself off the skeleton can be perceived! Nothing! This lasts about 15 minutes. Just before the body would fall to ground out of the skeleton the insect slowly bands up (Fig. 7 - from 9:56 to 9:57) and grabs the grass stalk with its front legs and becomes motionless again. Now the body is in the head-up position. At the same time its wings start to expand from two crumpled lumps of green tissue to beautiful, fully developed translucent wings. At the beginning, both wings are held in a single plain, but about 10 min later the second active motion of the insect happens. It puts its wings in parallel to its body as it is usual with the grownup insects. Then it is again motionless for more than an hour. Motionlessness is no doubt the best possible defense against predators in a dangerous state where the insect is fully exposed but cannot fly yet. Its 'take off' into grownup life comes all of a sudden without the slightest forewarning sign. No stretching of limbs, no turning the head, no attempts to move or 'test' the wings nothing, absolutely no 'learning curve'. It flies away abruptly with its full speed right in the closest dense bushes. It knows exactly where they stand and its five eyes already master the demanding navigation among thousands of branches and twigs.Ref.:(1) Fauna Europas, Bestimmungslexikon, George Westermann Velag, Brounschweig (1997), translated to Slovenian, Mladinaka Knjiga, Ljubljana (1981), pp 365.(2)
www.cicadasong.eu/cicadidae/lyristes-plebejus.html (songs) (accessed August 2. 2023)
