Tischeria caucasica Klasinski & Stonis, 2020

Alipanah, Helen, Nieukerken, Erik J. van, Farahani, Samira & Buszko, Jaroslaw, 2022, Tischeriidae (Lepidoptera) leafminers new to Iran, including Tischeria caucasica on Quercus: a sibling species of T. ekebladella or a case of clinal variation?, Nota Lepidopterologica 45, pp. 9-32: 9

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Tischeria caucasica Klasinski & Stonis, 2020


Tischeria caucasica Klasinski & Stonis, 2020  

Diagnostic remarks.

Tischeria caucasica   is very similar to T. ekebladella   (Fig. 1A-C View Figure 1 ). However, as stated by Klasiński et al. (2020), males can easily be distinguished from T. ekebladella   and T. ekebladoides   Puplesis & Diskus, 2003 by the unique, very long and distally bifurcate appendages of the juxta (Fig. 2A-H View Figure 2 ).

In the dissected males of T. caucasica   from Iran, there is some variation in the shape and length of the horn-like appendages of the juxta. Based on the results of this study, the apex of the longer pair of juxtal appendages is not always bifurcated. In some of the examined males, both appendages have bifurcated tips (Fig. 2A, F View Figure 2 ); while in some others the shorter one has simple and longer one has bifurcated tip (Fig. 2B, D, E View Figure 2 ). This has also been illustrated by Klasiński et al. (2020: 15, figs 15, 21-23), although without any explanation of the variation. Moreover, as we revealed in this study, the longest appendage of the juxta if bifurcated apically, the two branches are either assymetrical or symmetrical (Fig. 2A, B, D View Figure 2 , -F).

According to Klasiński et al. (2020), the two very long horn-like processes of juxta are bent basally; however, as we discovered in this study, the shorter one is always bent at its distal two-thirds, but the longer process is usually curved internally (Fig. 2A-F View Figure 2 ). Additionally, the anterior tip of the triangular ventral plate of vinculum varies from narrow (Fig. 2A View Figure 2 ) to relatively wide (Fig. 2B, D View Figure 2 ).

In the genitalia of examined females, as described by Klasiński et al. (2020), the antrum has a weakly sclerotized anterior margin with a unique membranous part, and the shortest prela has a wide base (Fig. 3A-D View Figure 3 ); however, the corpus bursae is not always heavily folded longitudinally (Fig. 3A View Figure 3 ).

No external difference between T. caucasica   and its closely related species was reported by Klasiński et al. (2020). Based on the results of this study, T. caucasica   is close to both T. ekebladella   and T. ekebladoides   in wing pattern and size. However, there are a few differences between T. caucasia   and T. ekebladella   (Fig. 1A-C, E-G View Figure 1 ): 1) T. caucasica   has a partly less pointed hindwing compared with T. ekebladella   ; 2) Fringes of the hindwing in T. caucasica   are slightly paler than in T. ekebladella   ; 3) Ventro-apical fringes of forewing in T. ekebladella   are slightly darker than in T. caucasica   and 4) On the underside of the forewing, the costal area at the apex is slightly paler in T. caucasica   compared with that of T. ekebladella   .

Tischeria caucasica   differs from T. ekebladoides   in the following external features (Fig. 1A, B, D View Figure 1 ): 1) T. caucasica   has a wider and less pointed hindwing compared with T. ekebladoides   ; 2) The ground colour of the body and forewing in T. caucasica   are darker than in T. ekebladoides   ; 3) In T. ekebladoides   the frontal tuft and collar area have scattered brown scales and 4) The forewing of T. ekebladoides   is slightly narrower than that of T. caucasica   .

Based on the results of this study, the female of Iranian T. caucasica   population has a slightly longer forewing than the male (Fig. 1A, B View Figure 1 ), with no significant difference between the two generations. Forewing length in the first generation was 3.5-4.6 mm (x = 4.11 mm ± 0.26, n = 44) in the male and 3.6-4.9 mm (x = 4.37 mm ± 0.26, n = 49) in the female. In the second generation it was 4.0-4.4 mm (x = 4.12 mm ± 0.16, n = 8) in the male, and 4.0-4.7 mm (x = 4.31 mm ± 0.25, n = 7) in the female.

Leafmines of T. caucasica   cannot be separated from those of T. ekebladella   . Moreover, the larvae of these two species are indistinguishable externally.

DNA Barcoding.

A Neighbor Joining tree is provided for barcodes of T. caucasica   and T. ekebladella   , together with barcodes of the other European species T. dodonaea   Stainton, 1858 and T. decidua   Wocke, 1876 (Fig. 11 View Figure 11 ). Each species has its own BIN, and is recognizable by its DNA barcode, except the pair T. caucasica   and T. ekebladella   . Unfortunately no barcodes are available for T. ekebladoides   .

DNA barcodes of two Iranian specimens appeared to be identical to that of a Dutch specimen of Tischeria ekebladella   and fall within one BINBOLD:AAF8247, that includes also all other available T. ekebladella   barcodes. The barcode of a Georgian larva from leafmines examined by EvN ( RMNH.INS.31425) groups with the Georgian adult of T. caucasica   (GBRD286), together as sister to all remaining T. ekebladella   and somewhat different from the Iranian T. caucasica   . Within BINBOLD:AAF8247 the average distance is 0.38% and the maximum distance is 1.93% (n = 54). The nearest neighbor is BOLD:ACU6278, representing the East Palearctic Tischeria siorkionla   Kozlov, 1986, with a distance of 8.01%.

Description of immatures.

Last instar larva (Fig. 4A-I View Figure 4 ) pale yellowish green, with pale light-brown head, pronotal and anal plates slightly darker than body. Head flattened with almost 5-6 stemmata arranged linearly, two posterior ones with a relatively larger distance to the remaining ones (Fig. 4C View Figure 4 ). Hairs and bristles distributed as in T. ekebladella   (for comparisons with that species refer to Grandi 1929, 1931, 1933, which are virtual identical descriptions).

Labrum (Fig. 4G View Figure 4 ) rectangular, and trilobed distally, with the two lateral lobes protruded considerably beyond median one, and a pair of fronto-lateral bristles; lateral and sub-posterior elements and medial ones represented by very small hairs, barely visible at very strong magnification. Mandible (Fig. 4F, H View Figure 4 ) sub-triangular, slightly longer than wide, tridentate apically with blunt tips; oral margin of mandible at proximal half with some setiform processes bent backwards and of different lengths (only visible under very large magnification). Maxillae (Fig. 4I View Figure 4 ) as in T. ekebladella   , with large laminar stems provided with two very minute placoid structures, its detailed structure hardly visible under available magnification. Maxillary palpi (Fig. 4I View Figure 4 ) composed of three articles, decreasing in width towards the apex. Labium (Fig. 4I View Figure 4 ) nearly as that of T. ekebladella   , but bi-articulated labial palpi were hardly visible under the available maximum magnification.

Antennae (Fig. 4H View Figure 4 ) three-segmented, segment 1 sub-cylindrical, slightly less than twice as long as wide, segment 2 slightly longer than wide, slightly less than half length of segment 1; distally with a long bristle, bristles on antennal surface hardly distinguishable under available magnification.

Thorax and abdomen. Nearly as in T. ekebladella   ; however, first thoracic segment not wider than other two (Fig. 4A-E View Figure 4 ). In the examined larvae the 2nd and 3rd thoracic segments mostly with same width and length (although in some specimens segment 2 is slightly wider than 3), segment 1 always the shortest, its width slightly less than two remaining thoracic segments or occasionally with same width (Fig. 4A-E View Figure 4 ). Abdominal segment 1 normally shorter than segments 2-6 (Fig. 4A, B View Figure 4 ), but in some specimens segments 1 and 2 equal in length and shorter than segments 3-6 (Fig. 4D View Figure 4 ). Abdominal segments 3-6 and sometimes 2-6 are usually the longest. Abdominal segment 1 usually slightly narrower than 2-6 or 3-6 (Fig. 4A, B, D View Figure 4 ).

Thoracic segments each with pair of very slightly sclerotized circular to elliptical plates on both dorsal and ventral surfaces towards the lateral sides (Figs 4D, E View Figure 4 , 5A, B, F View Figure 5 ). The plates of the 2nd and 3rd tergites and sternites have nearly the same size and shape, and if elliptical positioned transversely. The plates of the 1st tergite are elongate and somehow obliquely arranged to the longitudinal axis of the body (Figs 4D, E View Figure 4 , 5A View Figure 5 ); while those of the 1st sternite are sometimes irregularly shaped (Fig. 5F View Figure 5 ). These plates usually have a less sclerotized centre and are hardly visible, but they can be observed after staining the abdomen (Figs 4D, E View Figure 4 , 5A, B, F View Figure 5 ).

Thoracic segments with single long bristle laterally, and pair of short bristles dorso-laterally (Fig. 5B View Figure 5 ). Thoracic legs nearly pyramid-shaped or finger-shaped (Figs 4D, E View Figure 4 , 5F View Figure 5 ), very short, bearing two microscopic internal hairs distally (Fig. 5F View Figure 5 ).

Abdominal tergites 1-8 with pair of long bristles on either side. Tergites 1 and 2 with two pairs of short bristles positioned rather medio-laterally, and nearly in a line (Fig. 5C View Figure 5 ). Tergites 3-6 with two pairs of short bristles, which are not in the same line and positioned more laterally, and two pairs of nearly short, robust asymmetrical bristles internal to the lateral pairs, implanted on a common base or with bases completely confluent (Fig. 5D, E View Figure 5 ). Tergites 7 and 8 each with a submedial hair. Tergite 8 with five pairs of long marginal hairs, and some serration towards the middle part. Four pairs of the prolegs on segments 3-6 atrophied, without any trace of crochets (Figs 4D View Figure 4 , 5G View Figure 5 ), but with three hairs externally (Fig. 5G View Figure 5 ). Last proleg provided with pair of linear series of crochets, which in specimens examined each contain between 20-24 elements. They are not in equal numbers normally (n = 3) (Fig. 5H View Figure 5 ). For measurements of head capsule and body see Table 1 View Table 1 .

Pupa (Fig. 6A-E View Figure 6 ) pale ochre to ochreous-brown, with brown scales at the dorsal surface of abdominal segments. The sex of the pupa can be easily recognised by shape of last abdominal segment (Fig. 6D, E View Figure 6 ). In the female, the paired triangular processes at the end of last abdominal tergum are slightly larger and closer to each other than in the male (Fig. 6D View Figure 6 ). Papillae anales of female genitalia usually visible. Female pupa slightly larger than male. Length of male pupa 3.70-4.40 mm (x = 4.06 mm ± 0.17, n = 22); female pupa 3.50-5.1 mm (x = 4.28 mm ± 0.43, n = 25).


Host plants: In Iran Quercus castaneifolia   , Q. infectoria   , Q. libani   , Q. macranthera   , and Q. robur   ( Fagaceae  ). In Peykan Shahr the percentage of infection in Q. robur   was very high (Fig. 7B-I View Figure 7 ), higher than in Q. infectoria   (Fig. 8A-C View Figure 8 ), and in the latter species it was higher than in Q. libani   (Fig. 8D, E View Figure 8 ). In Q. libani   the infection rate was very low (one or two mines on each leaf) (Fig. 8D View Figure 8 ). Mines from Georgia (one larva barcoded RMNH.INS.31425) that most likely belong to this species, were found on Q. petraea subsp. polycarpa   (Schur) Soó and Castanea sativa   Mill.

Based on the results of this study, T. caucasica   has two generations per year in Tehran province. The eggs are white-grey in colour, deposited on the upper side of the leaf near the mid-rib or on larger lateral ribs. The mines consist of milky white upper-surface primary flat blotches, sometimes with orange hues, and like T. ekebladella   , with no traces of preceding corridors (Figs 7A-K View Figure 7 , 8A-E View Figure 8 ). As they get older, they turn very pale brown (Figs 7A-H View Figure 7 , 8A-C View Figure 8 ). The cocoon was made nearly at the centre of each blotch (the so called nidus) and pupation took place within the mine. No frass was observed inside the mine (Figs 7G, K View Figure 7 , 8B, C View Figure 8 ).

Leafmines were observed in 2017 and 2018 from late May to the first half of December, when the blotches were very minute. The greatest number of the mines in the first generation appeared in the first half of June. Adults were observed in early to mid July, when the next generation would occur. In the first generation, many adults emerged and, as a result, the population density increased remarkably during the second generation. In November, during leaf fall, the last instar larvae were overwintering inside the blotches. Live larvae were observed, yet sedentary through a cut in the upper epidermis in winter at the height of the cold. They became active and pupated after the end of the cold weather period.

Four larval instars were estimated by measuring the width of the head capsule of each larval instar and applying Dyar’s law ( Dyar 1890). Body length and head capsule width, min-max (mean ± SE) in all larval instars, are shown in Table 1 View Table 1 .

Seasonal development.

In Tehran (Peykan Shahr) the activity period of T. caucasica   larvae started from the end of May and continued in two generations until the beginning of December. In the first generation during 2018, the 1st larval instar hatched late May (22nd) and feeding on leaf tissue within the mine. The first and second larval instars formed a short linear mine towards the leaf edge. Third instar larvae appeared at the end of May (27th) , the last instar nearly at the first half of June (10th), and adults emerged from mid June (16th) to the 1st of July.

The number of mines per leaf varies; in some cases there are as many as 12 mines (Fig. 8C View Figure 8 ). The first larval instar of the second generation appeared at the end of August (30th) and the last instar on late September. They overwintered as 4th instar larvae and remained quiescent until pupation in late May to early June. According to the results of this study, T. caucasica   had a severe outbreak between 2017 to 2019, despite spraying the trees and destroying the fallen leaves. In 2020, the infection was considerably lower, and there was no trace of infection in the garden until May 2021.

Two species of parasitic wasps, Brachymeria excarinata   Gahan, 1925 (family Chalcididae   ) and Aprostocetus   sp. (family Eulophidae   ) emerged from the mines.


Georgia ( Klasiński et al. 2020) and Iran (Tehran: Peykan Shahr; East Azarbaijan: Ainalou; Gilan: Molumeh; Mazandaran: Neka) (Fig. 9 View Figure 9 ).

Material examined.

Iran, Tehrān Prov., Tehrān, Peykan Shahr   , 35°44'27"N, 51°10'50"E, 1317 m, 33 ♂♂ 26 ♀♀, emerged 6, 9, 16, 19, 21, 23, 24.vi.2018, 11 ♂♂ 23 ♀♀, emerged 3, 6, 7, 10, 13.vii.2019 (first generation); 7 ♂♂ 8 ♀♀, emerged 9.xii.2018 (second generation), S. Farahāni leg., all reared from Quercus robur   (genitalia slides HA-2375, HA-2376, HA-2377, HA-2378, HA-2379, HA-2380, HMIM); Same locality   , 1 ♂, 1 ♀, emerged 11.vi.2016, genitalia slides EvN5029 (♂), EvN5030 (♀), specimens barcoded, RMNH.INS.25029, RMNH.INS.25030 ( RMNH); 2♂, 1♀, not pinned, same data, RMNH   .

East Āzarbāijān Prov., Arasbārān protected area, Āsheghlou to Vāyeghān Rd., near Āinalou, 38°58'4.3"N, 46°42'27.6"E, 513 m, 17.ix.2008, J. Buszko leg., Quercus macranthera   , 3 mines, 1 ♂ 2 ♀♀, emerged 16.-26.iii.2009, genitalia slide ♂ EvN5287, RMNH.INS.25287, RMNH, HMIM; Gilān Prov., Molumeh , 36°51'17.01"N, 49°55'48.60"E, 11.ix.2008, J. Buszko leg., Quercus macranthera   , 3 mines, 1 ♂ 1 ♀, emerged 17.iii.2009, genitalia slide ♀ EvN5291, RMNH.INS.25291, RMNH, HMIM GoogleMaps   .

Māzandarān Prov., Nekā, 36°30'16.7"N, 53°23'27"E, 530 m, 30.ix.2007, J. Buszko leg., Quercus castaneifolia   , 4 mines, 2 ♂♂ 2 ♀♀, emerged 20.-26.ii.2008, genitalia slides ♂ EvN5289, EvN5290, RMNH.INS.25289, RMNH.INS.25290, RMNH, HMIM GoogleMaps   .

Georgia, 1 ♂ Lesser Caucasus, Samtskhe-Javakheti, Borjomi, Kvabiskhevi , 8.vii.2019, Leo Vahatalo, Anssi Vahatalo leg., LepiLED, genitalia slide EvN5274, specimen barcoded, GBRD.286, Research Collection of Anssi & Leo Vahatalo   .

Leafmines most likely belonging to T. caucasica   : Adjara AR, Chakvistavi , 41°40'37"N, 41°52'23"E, 19.ix.2018, M.V. Kozlov & V. Zverev, Castanea sativa   , 7 mines, RMNH.INS.48084-48085 ( RMNH) GoogleMaps   ; Adjara AR, Chikuneti , 41°34'13"N, 41°51'46"E, 26.ix.2018, M.V. Kozlov & V. Zverev, Quercus petraea subsp. polycarpa   , 17 mines, RMNH.INS.48093- RMNH.INS.48095 GoogleMaps   ; Adjara AR, Zeda Chkhutuneti , 41°28'57"N, 41°51'46"E, 23.ix.2018, M.V. Kozlov & V. Zverev, Castanea sativa   , 1 larva RMNH.INS.31425 (barcoded), 5 mines, RMNH.INS.48128-48129 ( RMNH) GoogleMaps   .

Material examined for comparison