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Lauterbornia 75: 1-13, D-86424 Dinkelscherben, 2012-12-03
Oligostomis reticulata (Linnaeus, 1761) (Trichoptera, Phryganeidae)
recorded again in The Netherlands and Belgium
Maria Judith Sanabria, Koen Lock, Mark Scheepens and David Tempelman
With 20 figures and 3 tables
Keywords: Oligostomis, Trichoptera, Insecta, macroinvertebrates, The Netherlands, Belgium, faunistic record, distri-
bution, phenology, habitat, frequency, identification, endangerment, larva, imago, faunistics
Schlagwörter: Oligostomis, Trichoptera, Insecta, Makroinvertebraten, Niederlande, Belgien, Fundmeldung, Verbrei-
tung, Phänologie, Habitat Frequenz, Bestimmung, Gefährdung, Larve, Imago, Faunistik
The caddisfly Oligostomis reticulata (Phryganeidae) was known to occur in both The Netherlands and Belgium,
with about 10 records from each country. The last published records dated back to the 1950’s. All previous re-
cords were based on adults. In 2009–2011, the species was found again in both countries. So far, this concerns
five localities: from The Netherlands, both larvae and adults were found at Neterselse Loop, a small stream in
the south of the country, Brabant province. From Belgium, the species has been observed from the Wijnendale
forest near Torhout, the Krankelbossen near Putte, De Maten near Diepenbeek and Buitengoor near Mol.
Their habitat is probably not very well covered in monitoring programmes. In addition, the species flies mainly
in April and is not known from light trapping since it is active during the day. So possibly, the species is less
rare than previously thought. More fieldwork is necessary to assess the status of this beautiful species.
1 Introduction
The caddisfly Oligostomis reticulata is a very rare species in The Netherlands. According to the
Dutch Trichoptera Distribution Atlas, the last record dated back to 1952 (Higler 2008). The
reported status of this species was "very rare/disappeared". The species is also included in the
Dutch Red List of caddisflies as "critically endangered" (Ministerie van LNV, 2001). Also in
Belgium, the species seemed to have disappeared. The last sighting was from Heusden (near
Ghent) in 1949. Recently, both in The Netherlands and in Belgium, the species was found
again: several larvae were found in 2010 in the Neterselse Loop, a stream in the south of The
Netherlands and adults have been photographed in Belgium in 2009, 2010 and 2011 at four loc-
alities. Due to its presumed rareness and these recent records, the purpose of this study is to
summarize the current knowledge on this species.
In Europe, the species is rather widely distributed: it is found in Germany, France, Finland,
Austria, Sweden and Denmark. The populations are generally small and isolated. The altitud-
inal range fluctuates between 10 and 800 m (Schmidt-Kloiber & Hering 2012).
The life cycle of Oligostomis reticulata is univoltine. The adults fly during the day, mainly from
April to May. The females lay eggs along the water edges. After the eggs have been deposited,
the water usually dries up and the eggs go into a state of quiescence. This stage lasts until the
end of September and the larvae grow from October until the end of February. Pupation takes
place in March (Timm & Sommerhäuser 1994). The habitat preference of this species is the lit-
toral zone of streams, secondary arms, lakes and temporary water bodies. The larva is found
between macrophytes and particulate organic matter. The larvae feed on algae, plant tissue and
βsediment. Most of the findings are in locations with -mesosaprobic and slightly acidic waters
(Graf et al. 2008).
2
2 Historical observations from The Netherlands
In The Netherlands, the first solid and clearly dated observation was made by C. Ritsema on
18 April 1919 in the Lage Steeg near Wageningen (det. Albarda). In 1934, Fischer published his
survey of the Dutch Trichoptera (Fischer 1934). Figure 1 shows how he listed these records.
Until now, 10 historical records from nine different localities are known from The Nether-
lands. These are presented in Table 1, which also includes the recent records.
Fig. 1: Reproduction of the first observations of Oligostomis reticulata from The Netherlands, recorded
as N. reticulata (= Neuronia reticulata) in Fischer (1934). Collectors’ names have been abbreviated: F. =
J. C. J. Fischer, D. C. G. = D. C. Geijskens, v. M. d. R. = A. B. van Medenbach de Rooy and Rits. = C.
Ritsema. Fischer further mentions a male specimen from the collection of the Zoological Museum in
Amsterdam (Z. M.), without indication of location
3 Historical observations from Belgium
From Belgium a dozen historical observations are known. The oldest documented observation
dates back to 28 April 1858 from the village of Herkenrode (Campine area, province of
Limburg). De Selys-Longchamps (1888) described this observation: "April, on the banks of the
Demer near Hasselt, Campine area, by Mr. E. Claes". The record is reproduced in figure 2.
Fig. 2: Reproduction of the first observation of Oligostomis reticulata, recorded as Neuronia reticulata
in De Selys-Longchamps (1888): "Campine area in April, on the banks of the Demer near Hasselt, by
Mr. E. Claes. Northern species, one of the most beautiful European Phryganeidae. Blackish brown legs
with yellowish hindtibia"
Most of these historical observations have been done in the Campine area, in the southern
part of the province of Limburg. The other observations are scattered over the country, with
only one record from Wallonia (Lienne, south of Liège). Table 2 summarizes all known re-
cords of the species in Belgium.
4 New records in The Netherlands: Neterselse Loop
On 27 October 2010, a macro-fauna sample was taken, using a dip net, at the Neterselse Loop
("Netersel" = the name of a nearby village, "Loop" = small stream). The stream is located in
the Neterselse Kempen, not far from the border with Flanders. In the sample, one larva of Oli-
gostomis reticulata was found. Figure 3 shows the larva in its case, figure 4 shows the case, which
is constructed of large pieces of leaves and is more or less rectangular in shape. The record con-
stitutes the first record of the species in The Netherlands in almost 50 years and is also the first
Dutch discovery of a larva of this species.
Tab. 1: Oligostomis reticulata. Observations from The Netherlands. GL = Gelderland, LI = Limburg, NB = Noord Brabant, OV = Overijssel
Location Province Latitude Longitude Altitude (m) Date Number Observed by Reference
Arnhem GL 51°58'27" 5°55'32" 9 ± 1900 1 adult A. B. van Medenbach de Rooy Fischer, 1934
Wageningen, Lage Steeg GL 51°57'58" 5°39'49" 10 18-04-1919 9 ♂, 1 ♀C. Ritsema Fischer, 1934
Wageningen GL 51°57'58" 5°39'49" 15 04-04-1920 1 ♂C. Ritsema collection RMNH-Leiden
Berlicum, Leigraaf NB 51°39'39" 5°26'42" 7 04-1927 1 ♀D. C. Geijskes Geijskes, 1932
Venray LI 51°30'56" 5°57'48" 22 17-04-1934 1 ♀J. C. J. Fischer Fischer, 1934
Ulvenhout NB 51°32'33" 4°46'54" 5 02-05-1940 1 ♂J. C. J. Fischer Fischer, 1940
Eindhoven NB 51°26'10" 5°28'25" 17 22-04-1951 1 ♂Neyts coll. Fischer, Rotterdam
Nuenen NB 51°27'47" 5°31'52" 17 13-04-1952 2 ♂Neyts coll. Fischer, Rotterdam
Buurse OV 52°08'15" 6°49'07" 35 14-04-1952 11 ♂J. C. J. Fischer coll. Fischer, Rotterdam
Hilvarenbeek, Spruitenstroompje NB 51°28'19" 5°09'04" 13 02-05-1962 1 adult H. K. M. Moller Pillot pers. comm. Moller
Bladel, Neterselse Loop NB 51°25'34" 5°12'42" 23 27-10-2010 1 larva M. J. Sanabria this paper
Bladel, Neterselse Loop NB 51°25'34" 5°12'42" 23 08-12-2010 1 larva M. J. Sanabria this paper
Bladel, Neterselse Loop NB 51°25'34" 5°12'42" 23 22-02-2011 5 larvae M. J. Sanabria this paper
Bladel, Neterselse Loop NB 51°25'34" 5°12'42" 23 15-04-2011 2 ♂, 2 ♀M. J. Sanabria & D. Tempelman this paper
Tab. 2: Oligostomis reticulata. Observations from Belgium. AN = Antwerpen, LG = Liège, LI = Limburg, OV = Oost-Vlaanderen, WV = West-Vlaanderen
Location Province Latitude Longitude Altitude (m) Date NumberObserved by Reference
Hasselt (Demer) LI 50°32'36" 4°24'44" 30 28-04-1858 1 E. Claes De Selys-Longchamps (1888)
Herkenrode LI 50°32'36" 4°24'44" 40 23-04-1888 1 E. de Selys-Longchamps De Selys-Longchamps (1888)
Herkenrode LI 50°32'36" 4°24'44" 40 28-04-1888 1 E. de Selys-Longchamps De Selys-Longchamps (1888)
Herkenrode LI 50°32'36" 4°24'44" 40 01-05-1888 1 E. de Selys-Longchamps De Selys-Longchamps (1888)
Melle OV 50°33'07" 3°00'03" 5 03-04-1910 3 M. Goetghebuer Stroot (1985)
Merelbeke OV 50°33'07" 3°00'03" 10 27-04-1917 2 M. Goetghebuer Stroot (1985)
Lienne LG 49°38'39" 4°23'12" 230 12-04-1933 1 n.n. (in KBIN collection)
Melle OV 50°33'07" 3°00'03" 5 04-04-1943 4 J. Verbeke Stroot (1985)
Heusden OV 50°33'07" 3°00'03" 5 14-04-1944 1 J. Verbeke Stroot (1985)
Schelderode OV 50°33'07" 3°00'03" 10 23-04-1943 8 J. Verbeke Stroot (1985)
Heusden OV 50°33'07" 3°00'03" 5 14-03-1945 1 J. Verbeke Verbeke J.
Melle OV 50°33'07" 3°00'03" 5 14-04-1946 1 M. Goetghebuer Goetghebuer M.
Kuringen LI 50°32'36" 4°24'44" 30 ?1947 1 n.n. Marlier (1947)
Genk LI 50°32'36" 4°24'45" 50 18-04-1947 1 G. Jacquemin Stroot (1985)
Torhout, bos van Wijnendale WV 51°04'08" 3°02'60" 20 04-04-2009 1 T. Calu http://www.wa arnemingen.b e/view/42652676
Torhout, bos van Wijnendale WV 51°04'08" 3°02'60" 20 18-04-2010 1 D. Deruytter http://www.wa arnemingen.b e/view/47442628
Torhout, bos van Wijnendale WV 51°04'08" 3°02'60" 20 25-03-2011 20 K. Lock this publication
Putte, Krankebossen AN 51°03'58" 4°39'46" 20 27-03-2011 6 P. Hendrickx http:// www.waarneminge n.be/view/53055140
Diepenbeek, De Maten LI 50°56'41" 5°26'29" 35 01-04-2011 1 D. Smets http://www.wa arnemingen.b e/view/53110725
Mol, Buitengoor AN 51°13'11" 5°10'10" 25 10-04-2011 2 P. & M. Wouters http://www.waarn emingen.be/ view/53345539
3
4
Fig. 3: Oligostomis reticu-
lata. Larva
Fig. 4: Oligostomis reticulata. Case made of piec-
es of leaves (laboratory photograph)
The larva of Oligostomis reticulata can be easily recognized by the distinctive U-shaped spot on the
frontal apotome and the two sclerites on the mesonotum (Fig. 5, 6).
The Neterselse Loop is a stream, located north of the village of Netersel. It stretches over
nearly 2 km. Its origin is at the Neterselse Heide ("heide" = moorland area). From there, it
flows in eastward direction and discharges in the Beerze at Westelbeers Broek. This is about
0,8 km downstream from the sampling point where Oligostomis reticulata was found.
The area is forested and has a natural character and management (Fig. 7, 8). The stream
looks quite natural, but it has been created in the course of the 19th century as the main drain-
age system of the moorland area. Being the main water body of this area, the stream almost
never dries out completely. During prolonged dry periods, a small seepage stream remains.
Before entering the main stream, a small tributary, originating from the moorland area,
flows through the forest and later passes a clearing (Fig. 8, background of the photo). Here,
several shallow ditches have been dug, which drain into the tributary. Molinia caerulea, Sphagnum
sp. and reed (Phragmites australis) are dominant here. The ditches were dry during our visits in
5
October and April. Along these ditches, 10–20 m next to the tributary, both Hagenella clathrata
and Oligostomis reticulata were found as adults. The tributary itself (sampling station: 295.114) is
an excavated watercourse and may be considered a ditch which has some water current. The
water depth varies from 10 to 50 cm. Its width fluctuates between 1 to 1.5 m. On 22 February
2011, current velocity was approximately 0.15 m/s. Its banks are half shaded. The trajectory
consists of a steep left bank and a faintly sloping right bank. The soil consists of sand with oc-
casional branches and wood. Locally, the stream bed is covered with coarse detritus and leaves.
Fig. 5: Oligostomis reticulata. Larva, lateral view
Fig. 6: Oligostomis reticulata. Head, pronotum and mesonotum in dorsal view, showing two distinctive
dorsal sclerites on the mesonotum (left) and the head with distinct markings (laboratory photographs)
6
The larva of Oligostomis reticulata was in the main stream (sampling station: 259.112, Fig. 7). The
stream width is 3 to 5 m. The water depth varies. On 27 October 2010, it reached 1 m. This is
probably a typical depth in autumn times, but it may be less than 0.2 m or almost dry during
prolonged dry periods. The current velocity in October 2010 was approximately 0.1 m/s.
7 8
Fig. 7: The Neterselse Loop near the Neterselse Heide, autumn 2010. This is the sampling location
where the larva of Oligostomis reticulata was collected.
Fig. 8: Small tributary of the Neterselse Loop, where flying adults of Oligostomis reticulata were found.
Photo 15 April 2011. Background: the clearing with the shallow draining ditches, where both Oli-
gostomis reticulata and Hagenella clathrata were recorded
The sediments consist of coarse sand containing large amounts of iron (coloring the stream
bed orange) and are rich in humic substances originating from the previously described tribu-
tary which directly drains water from the moorland area. Because of the humic acids, the wa-
ter color is dark brown. There is a dense canopy along the shores on both sides providing
shade. The stream bed is also covered with large amounts of coarse detritus, originating from
fallen leaves and small twigs. A broad-leaved pond weed species (Potamogeton sp.) and Callitriche
sp. are found in several places. The banks of the stream are very steep here, with concave
banks in places. In the same locality, hundreds of larvae of the caddisfly Glyphotaelius pellucidus
were also present.
From January-March 2011, physical and chemical parameters were monthly measured, show-
ing low dissolved oxygen and high ammonium and nitrate loads. They indicate a large amount
of nutrients present in the water. Table 3 summarizes these results, giving minimum and maxi-
mum ranges of selected parameters. On 22 February 2011, the species was found again: three lar-
vae were collected, one of which had its case closed and apparently preparing to pupate (Fig. 9,
10). On 15 April 2011, the area was visited once more. The weather was favourable: 15 ˚C,
7
Tab. 3: Physical and chemical parameters of the Neterselse Loop (sampling station 249.910), showing
ranges over January-March 2011
Location Temperature
(°C)
pH Conductivity
(μS/cm)
Dissolved oxy-
gen (%)
Kjeldahl nitro-
gen (mg/l)
Total nitrates
(mg/l)
249.910 0.2-7.3 6.2-6.5 349-381 65-73 1.4-3.1 6.2-12.0
9 10
Fig. 9 and 10: Oligostomis reticulata. Preparing to pupate: the larva closes its case with pieces of
leaves and small twigs in order to pupate. On the left photo (just right from the middle), a piece of a
Potamogeton has been used
11 12
Fig. 11: Oligostomis reticulata. Adult ♀ (Neterselse Loop, The Netherlands, 15 April 2011)
Fig. 12: An almost dried out, transverse drain 10–20 m away from the stream, where the adults of
Oligostomis reticulata were mainly observed sitting on leaves of Phragmites australis
8
rather sunny and almost no wind. After one hour of searching, a first adult of Oligostomis
reticulata was found along a lateral tributary of the Neterselse Loop (Fig. 11, 12). At exactly the
same locality – no more than 1 m away – an adult of Hagenella clathrata was also found.
In Oligostomis reticulata and Hagenella clathrata, the pattern and color of wings is almost the same.
However, with the naked eye, one can clearly see that Oligostomis reticulata has black legs and Ha-
genella clathrata yellow ones (Fig. 13, 14).
Fig.13: Oligostomis reticulata. Adult ♀ (Neterselse Loop, The Netherlands, 15 April 2011)
Fig. 14: Hagenella clathrata. Adult ♀ (Neterselse Loop, The Netherlands, 15 April 2011). Note the strik-
ing similarity in wing pattern, but also the difference in leg colo
One male and one female of Oligostomis reticulata and a male specimen of Hagenella clathrata were
collected. The identity of both species was confirmed by the structure of both male and female
genitalia (Fig. 15, 16). The general leg color, observed in the field, is indeed pitch black with
light color only on the hind tibia, approximately 80 % of which is light in color (Fig. 17).
9
Fig. 15: Oligostomis reticulata. ♂, genital structures in lateral, dor-
sal and ventral view (Neterselse Loop, The Netherlands)
Fig. 16: Oligostomis reticulata. ♀, genital structures in lateral, dor-
sal and ventral view (Neterselse Loop, The Netherlands)
Fig. 17: Oligostomis reticulata. ♀, hind leg (Neterselse Loop, The Netherlands)
5 New Belgian records
In both April 2009 and 2010, adults were photographed in the forest of Wijnendale, near Tor-
hout in West-Flanders. The photos were posted on Waarnemingen.be as "unknown caddisfly"
and were subsequently identified as Oligostomis reticulata, based on the characteristic wing pattern
in combination with the black legs (Fig. 18, 19). Later, on 25 March 2011, the species was re
10
corded again: dozens of animals were found
along the stream. The animals were photogra-
phed in a forest along a watercourse. Howev-
er, the species was lacking on parts of the wa-
tercourse that were overgrown with thickets
of blackberries. The new location is some 50
km west of the westernmost "historic loca-
tion" near Ghent.
Fig. 18: Habitat in the forest of Wijnendale where
Oligostomis reticulata was found
Fig. 19: Oligostomis reticulata. Adult, Forest of Wijnendale, Belgium, 25 March 2011
In 2011, the species was also photographed in three other areas: the Krankelbossen near Putte,
De Maten in Diepenbeek and Buitengoor near Mol. Again, observations were posted on
Waarnemingen.be, after which the species could be identified.
11
6 Distribution and discussion
In figure 20, all known observations of Oligostomis reticulata from both The Netherlands and Bel-
gium have been combined. As for The Netherlands, we now know of one extant population;
in Belgium four existing populations are known. The map shows that these populations are
very localized and therefore may be considered as threatened.
The new observations in 2009, 2010 and 2011 of Oligostomis reticulata, for the first time over
half of a century in both Belgium and The Netherlands, are striking. The species was classified
as "very rare/disappeared"(Higler, 2008).
Fig. 20: Oligostomis reticulata. Historical (dots) and new records from 2009–2011 (stars) in The Nether-
lands and Belgium
The fact that the species "suddenly" shows up in five separate areas is not easily explained. In
both The Netherlands and Flanders, intensive sampling of lowland streams has been carried
out by (or commissioned by) their respective waterboard authorities. Since the 1980’s, thou-
sands of macrofauna samples have been processed, without finding a single larva of this spe-
cies. However, routine sampling is normally performed on accessible places (parking of labor-
atory vehicle) and only permanent waters are sampled. This suggests that micro-habitats
where the larvae live are easily missed.
Timm & Sommerhäuser (1994) carried out an elaborate research on the biology of this spe-
cies. They found that the species is on the wing in April. Eggs are present in May. Over June-
mid September, the species is in quiescence. Larvae appear from mid September only and can
be found until mid February. From mid February to March, the species is in the pupal stage,
12
emerging in April. This phenology explains why the species is missed in routine sampling,
which is usually carried out from April to September. Early in the sampling season, the spe-
cies is only found as adult; it than oversummers as egg, making it impossible to catch. In
September, only small, newly hatched larvae may be encountered. The first record of a larva
was done within the framework of a special project studying the ecology of the Neterselse
Loop and the macrofauna sample was taken "off season", in mid October 2010. The adults
emerge in early spring and are never captured by light. So the species also eludes traditional
light trapping and as it normally disappears by May, one can easily miss it.
Despite the fact that the species is missed as larva during routine sampling schemes and
eludes light trapping, it suddenly shows up in new localities. Social websites like Waarnemin-
gen.be, where any observer can post records and images of insects, may indeed become sources
of faunistic knowledge, showing that records no longer come from a handful of specialists but
from thousands of nature enthusiasts. It is a rather large, beautiful and diurnal species - a grate-
ful object for photographers.
The new records shed some light on their habitat and ecology. They are quite consistent
with remarks found in the literature. The larva of this caddisfly is usually found in slowly
flowing waters with plenty of organic material such as leaves and twigs. The larvae feed on
coarse organic material and plants and construct their cases of rectangular pieces of leaves. The
larvae are omnivores. The adults are found from March to May and are diurnal (Higler, 2008).
The new records show that the presence of forest is important for the presence of the species.
In both the Neterselse Loop and the forest of Wijnendale, the species was found in streams
with a moderate flow, but also periodic dryness in the summer. Both streams are actually not
without human impact. The water quality is fair but not extraordinary.
The question still remains whether the historical populations still exist. Several areas have
probably been lost, as large parts of both countries have gradually been converted into build-
up areas. A problem also is to find the exact localities, as historical records usually only men-
tion the nearest village or town – the actual sampling locality being somewhere in a circle of
about 5 km around the village centre. Further study – especially field study – is needed to de-
termine how rare this species really is.
Acknowledgements
The authors wish to express their gratitude to Johann Waringer (University of Vienna) for comments on this article,
Wolfram Graf (University of Agricultural sciences, Vienna), for confirming the identification of Oligostomis reticulata,
André van Loon (EIS-Nederland, Leiden) for providing the known observations in The Netherlands, Henk Moller
Pillot (Tilburg) for summarizing the records from the 1960’s and commenting on the description of the Neterselse
Loop and Edwin Verduin (Grontmij) for producing the distribution map. Sampling at the Neterselse Loop and labor-
atory work was carried out by AQUON-Institute for Research and Consultancy and was commissioned by the local
waterboard authority of Waterschap de Dommel. The authors are grateful this work has been made possible by their
respective employers. Our thanks are also due to the people posting their valuable observations at Waarnemingen.be.
References
De Selys-Longchamps, E. (1888): Catalogue raisonné des Orthoptères et des Nevroptères de Belgique.- Annales de la
Société Entomologique de Belgique 23: 103-203, Bruxelles
Graf, W., J. Murphy, J. Dahl, C. Zamora-Muñoz & M. J. López-Rodríguez (2008): Distribution and Ecological Prefer-
ences of European Freshwater Organisms. Volume 1 - Trichoptera. Edited by Schmidt-Kloiber, A. & D. Hering.-
388 pp., (Pensoft Publishers) Sofia, Moscow
Fischer, F. C. J. (1934): Verzeichnis der in den Niederlanden und dem Nachbargebiete vorkommenden Trichoptera.-
Tijdschrift voor Entomologie 77: 177-201, s'Gravenhage
Graf, W., Murphy, J., Dahl, J., Zamora-Muñoz, C., López-Rodríguez M.J. & Schmidt-Kloiber., A. (2006): Trichoptera
Indicator Database. Euro-limpacs project, Workpackage 7 - Indicators of ecosystem health, Task 4, www.fresh-
waterecology.info, version 5.0 (accessed 15 June 2012)
13
Graf, W. & Schmidt-Kloiber, A. (2011): Additions to and update of the Trichoptera Indicator Database. www.fresh-
waterecology.info, version 5.0 (accessed 15 June 2012)
Higler, L.W.G. (2008): Verspreidingsatlas Nederlandse kokerjuffers (Trichoptera). Uitgave EIS-Nederland. Leiden,
248pp.
Minsterie van LNV (2001): Rode Lijst kokerjuffers. Website: www.minlnv.nederlandsesoorten.nl (accessed February
2011)
Schmidt-Kloiber A. & Hering D. (eds.) (2012), Website: www.freshwaterecology.info - the taxa and autecology data-
base for freshwater organisms, version 5.0 (accessed 15June 2012)
Timm, T. & M. Sommerhäuser (1994). Beitrag zur Phänologie und Ökologie von Oligostomis reticulata (Trichoptera,
Phryganeidae), einer seltenen Köcherfliege der Niederrheinischen Sandplatten.- Verhandlungen. Westdeutscher
Entomologentag, Nachtrag 1993: 79-85, Düsseldorf
Waarnemingen.be Website: www.waarnemingen.be (accessed February 2012)
Figures
The figures 3,4,8,9,10 are made by Maria Judith Sanabria; figures 11,12,13,14,15,16 and 17 are made by David Tempel-
man; figure 7 is from Mark Scheepens; figures 18,19 are made by Koen Lock. Figure 20 is made by Edwin Verduin
(Grontmij).
Adressess of the authors:
Msc. Maria Judith Sanabria, AQUON. Instituut voor water onderzoek en advies (m.sanabria@aquon.nl)
Dr. Koen Lock, Gent (koen_lock@hotmail.com)
Mark Scheepens, Waterschap De Dommel (MScheepens@dommel.nl)
David Tempelman, Grontmij|team Ecologie (david.tempelman@grontmij.nl)
Received: 2012-06-17
Accepted: 2012-06-28
