Water lily borer

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Water lily borer
Water lily borer (Elophila nymphaeata)

Water lily borer ( Elophila nymphaeata )

Systematics
Order : Butterflies (Lepidoptera)
Superfamily : Common moth (Pyraloidea)
Family : Crambidae
Subfamily : Acentropinae
Genre : Elophila
Type : Water lily borer
Scientific name
Elophila nymphaeata
( Linnaeus , 1758)
Specimen from the Koenig Museum
Caterpillar with caterpillar quiver

The elophila nymphaeata or pondweed borer ( elophila nymphaeata ) is a butterfly ( moth ) from the family of Crambidae and belongs to the subfamily acentropinae . The caterpillars develop mostly under water, which is unusual for butterflies.

features

The wingspan is 17 to 28 millimeters. The basic color of the upper side of the forewings is white with light brown to dark brown markings made up of transverse lines, dark-edged spots and jagged bands. Usually the subbasal transverse line is still relatively clearly developed. Often it has an outwardly directed line or narrow tooth in the middle. The inner transverse line is only faintly drawn, often almost extinguished. The outer transverse line is also only weakly indicated, often as an outwardly directed, often interrupted zigzag band. Between the inner and outer transverse line there are several large, rounded, light to dark-edged, white spots. A transversely oval to crescent-shaped spot near the outer transverse line, which sits close to the Kostal rim and is open to the Kostal rim, is very clearly formed. Another more rounded spot sits closer to the inner transverse line and closer to the inner edge of the wing. Two further small spots are developed approximately at the level of the discal spot and at the costal margin on the inner transverse line. They are also open in the ground towards the Kostal edge, but are crossed by a longitudinal line that runs parallel to the Kostal edge to just under the outer transverse line. In the area of ​​the submargin line there is a series of elongated whitish dots which are mostly jagged inwards and which are bordered on the outside by a dark transverse line. The hem field is light to dark brown, the hem line is often highlighted in dark brown. The fringes are light gray-brown (lighter than the fringe, but clearly darker than the basic color of the forewing).

The rear wings are also white in the basic color. The drawing is more constant and clearer here. It consists of a strong inner transverse line and a strong, inside strongly receding and outwardly white lined outer transverse line. The middle field is almost pure white and has only two strong discal spots. The submarginal line is usually developed as a broad brown, outwardly directed zigzag band. The hemline is usually clearly drawn dark. The fringes are lighter than the hemline, often irregularly piebald. The moths have a well-developed proboscis.

The drawing of the somewhat larger females is usually somewhat weaker than that of the males.

The eggs are yellowish when deposited. They are flattened lens-shaped.

The caterpillars are about 22 millimeters long and have a yellowish to light green color. They are only slightly hairy.

The doll is 10.0 millimeters long and 3.0 millimeters in diameter. The only slightly shiny pupa is light brown and moderately stocky. The cremaster is relatively short; it has three pairs of almost equally large, dark, stiff bristles.

Geographical distribution and habitat

The water lily borer is widespread in the northern hemisphere (Holarctic), wherever suitable habitats are available. The distribution area of ​​the species extends from northwestern North Africa to northern China, the Russian Far East and Japan (here with the subspecies E. nymphaeata ezoensis ). In northern Europe, the area extends to the British Isles and northern Sweden . In Asia the species occurs south to Asia Minor , Cyprus and the Middle East as well as in Iran , Uzbekistan and Afghanistan .

The water lily borer lives mainly in small, stagnant bodies of water such as ponds, ditches and ponds and is widespread and frequent in Central Europe .

Way of life

The water lily borer forms two generations a year in Central Europe, with the first generation moths flying in June and the second generation moths in August and September. Up to three generations are trained in southern Europe. During the day, the moths hang upside down or upside down on or under plants of the bank vegetation. They are crepuscular and nocturnal and come to artificial light sources. They stay in areas of the shore region with high humidity, while sunlit, dry areas with little humidity are avoided. The evening activity also depends on the occurrence of the " dew fall " (= exceeding the 100% saturation limit). Therefore, on some days the moths are already active hours before sunset, while on other days they are actually only active in or even after dusk. The activity of the moths is also temperature-dependent. In the evening temperatures below 10 ° C, the moths do not fly at all. During the night, activity stops when the temperature drops below 11 ° C. Under favorable conditions, the maximum flight activity is reached approx. 60 - 70 minutes after sunset. The males fly around 10 to 20 centimeters above the water level. After only a short search flight, the females attach themselves to a pondweed flower or a plant stem. The males are attracted by pheromones; copulation takes place at the resting place of the females. Mating takes 20 to 40 minutes; after mating, both partners fly back to shore.

Oviposition begins 15 to 20 hours after copulation in the afternoon of the following day. After a search flight, the female lands on a pondweed or lily pad. This must be wider than the span of the female's legs. The female then pushes her abdomen under the leaf. The eggs are laid in layers on the host plants just below the water level. The clutch sizes are very different (from over 400 to very few; about 3 eggs). The average number of eggs laid per female is approx. 340 eggs. The male moths live to be up to 18 days old, on average 11 days, while the female moths die 2 to 3 days after oviposition.

The caterpillars hatch after 10 to 11 days (at almost 20 ° C mean water temperature). In cool weather, the time of hatching can be delayed by a few days (up to approx. 14 days). Most egg caterpillars leave the immediate vicinity of the clutch and crawl to neighboring leaves on the underside of the surface tension . Some of the young caterpillars initially mine in stems and leaves. Other egg caterpillars feed directly on the leaves. The mining stage lasts a maximum of four days. They then make small, weakly spun quivers from 4 to 6 millimeters long and 2 to 3 millimeters wide pieces of leaf. The quivers are filled with water and attached to the underside of the leaf on which the caterpillars feed. During this phase, the caterpillars breathe through the skin surface.

According to the two generations, caterpillars can be found from May and then again from August. They feed on swimming pondweed ( Potamogeton natans ), water knotweed ( Polygonum amphibium ), water lilies ( Nymphaea ), common hedgehog ( Sparganium emersum ) and small duckweed ( Lemna minor ). The first generation caterpillars become hydrophobic after two hydrophilic stages; there are two more caterpillar stages up to pupation.

The second generation caterpillars grow more slowly than the first generation caterpillars due to the slowly falling temperatures in September and October. From a water temperature of 10 to 11 ° C they stop eating. They wander with their quiver along the stems to a depth of 20 to 50 centimeters. There they attach the quiver to the stem that is still green and drill a 10 to 15 millimeter long passage into the core of the stem. Reichholf found the overwintering caterpillars only in the stalks of the swimming pondweed ( Potamogeton natans ). An important prerequisite for successful wintering is that the stems were still green in spring and not rotten. Even the temporary drying out does not harm the overwintering caterpillars. In spring, the caterpillars leave their stalk hiding place and crawl up the stalks. They make a new quiver from the leaves of the previous year and start to eat at every accessible green leaf. After a few days they molt and the caterpillars become hydrophobic , i.e. H. the surface of the caterpillar is no longer wetted, but is surrounded by an air cushion. The caterpillar repeatedly stretches its front end into the air and renews the air in its quiver by moving its front body back and forth. The hydrophobic substances very likely come from the caterpillars' diet, because shortly before they switch from hydrophilic to hydrophobic, they eat on the tops of the leaves of the pondweed or water lily, which are hydrophobic. If hydrophobic caterpillars are fed with lettuce or hydrophilic aquatic plants, they become hydrophilic again. Repeated feeding with hydrophobic aquatic plants leads to the hydrophobicity of the caterpillars again. The hydrophobic caterpillar also makes a container from two elliptical pieces of leaf that are spun together by spun threads. It is renewed six to eight times during a caterpillar stage, and the leaf pieces are always cut out somewhat larger. It contains air, the penetration of water is prevented by the tightly spun edges and a fine coating of spun threads inside the quiver. The quiver is pulled behind when crawling; the caterpillar sticks its head out of the container to eat. The caterpillars moult one more time with a body length of around 17 to 19 millimeters. They are fully grown at the end of May and are now making a special doll's quiver. This is attached to the stems of the host plant at a depth of about 1 to 12 centimeters below the water surface. Usually the last caterpillar quiver is used and simply spun together tightly. A new quiver is made less often. In the literature it can often be read that the caterpillar bites the plant tissue in order to obtain oxygen from the aerenchyme of the plant. However, the pupa does not need any oxygen from the plant tissue and biting the stems only serves to better attach the pupae's quiver to the plant. The pupae rest for 12 to 16 days, depending on the water temperature. The moths hatch from their pupa cocoons under water from late May to early June. The moth is protected from wetting by special scales that are long, narrow and almost hair-shaped. After surfacing, it first runs like a water strider on the surface membrane of the water to the next leaf. They rest there until the meconium is eliminated .

In the overview, the average development time for the summer generation is:

  • Egg stage (until hatching): 10 days
  • hydrophilic caterpillar (2 stages): 20 to 25 days
  • hydrophobic caterpillar (2 stages): 25 to 30 days
  • Doll rest: 12 to 16 days;

d. H. a total of 70 to 80 days from egg-laying to hatching of the butterfly.

Systematics and taxonomy

The species was first scientifically described by Carl von Linné in 1758 under the name Phalaena Geometra nymphaeata . It is the type species of the genus Elophila Huebner, 1822. In older publications it also appears in the combinations Nausinoe nymphaeata and Nymphula nymphaeata . Speidel (2005) distinguishes five subspecies:

Chen, Wu and Xue (2010), on the other hand, list ezoensis Yoshiyasu, 1985 under the synonym of Elophila nymphaeata nymphaeata , so that it can be assumed that they only accept four of the five subspecies mentioned above (plus an unnamed subspecies from Ireland). According to this view, the area of ​​the nominotypical subspecies would extend to Japan and northern China.

swell

Individual evidence

  1. ↑ Speidel Goater et al. (2005: pp. 43–46)
  2. ↑ Females laying eggs
  3. ^ R. Barbier and G. Chauvin: The Aquatic Egg of Nymphula nymphaeata (Lepidoptera: Pyralidae) On the Fine Structure of the Egg Shell. Cell and Tissue Research, 149 (4): 473-479, 1974 doi : 10.1007 / BF00223026
  4. ↑ Jan Patočka: The pupae of the Central European borer (Lepidoptera: Pyraloidea, Pyralidae). Subfamilies Acentropinae, Odontiinae, Evergestinae and Pyraustinae. In: Linz biological contributions. 33rd volume, issue 1, Linz 2001, pp. 347-405 ( PDF on ZOBODAT ).
  5. ^ Reichholf (1970: p. 687ff.)
  6. ^ Carl von Linné: Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. 10th edition, Stockholm 1758 Online at SUB Göttingen (description of the species p. 529)
  7. ↑ Hannemann (1964: p. 274)
  8. ^ VV Dubatolov, AN Streltzov: New records of pyralid moths (Insecta, Lepidoptera, Pyraloidea) in the Lower Amur. In: Amurian zoological journal. II (1), 2010, pp. 57-60 ( PDF on eco.nsc.ru; Russian).
  9. ↑ Chen et al. (2010: pp. 41–43)

literature

  • Barry Goater, Matthias Nuss, Wolfgang Speidel: Pyraloidea I (Crambidae: Acentropinae, Evergestinae, Heliothelinae, Schoenobiinae, Scopariinae) . In: P. Huemer, O. Karsholt (Ed.): Microlepidoptera of Europe. 4: 1-304. Apollo Books, Stenstrup, 2005, ISBN 87-88757-33-1
  • Hans-Joachim Hannemann: Small butterflies or Microlepidoptera II. The curlers (sl) (Cochylidae and Carposinidae). The moth-like (Pyraloidea). In: Friedrich Dahl: The animal world of Germany and the adjacent parts of the sea according to their characteristics and their way of life. Part 50., VEB Gustav Fischer Verlag, Jena 1964.
  • Josef Reichholf: Studies on the biology of the water butterfly Nyrnphula nymphaeata L. (Lepidoptera. Pyra1idae). International Review of the Entire Hydrobiology and Hydrography, 55 (5): 687-728, 1970, doi : 10.1002 / iroh.19700550502 .
  • Helgard Reichholf-Riehm: Butterflies . Orbis Verlag, Munich 2000, ISBN 3-572-01084-5 , 287 pages.
  • František Slamka: The common moth (Pyraloidea) of Central Europe: determination - distribution - flight area - way of life of the caterpillars. 2nd partially revised edition, Bratislava 1997, ISBN 80-967540-2-5 , 112 pages.

Web links

Commons : Water lily borer  - album with pictures, videos and audio files