Entedon costalis Dalman, 1820

Gumovsky, Alex V., 2008, Parasitism of Entedon costalis (Hymenoptera: Eulophidae) in Glocianus punctiger (Coleoptera: Curculionidae): an example of intentional discovery of the parasitoid-host association, Zootaxa 1964 (1), pp. 40-68 : 47-52

Entedon costalis Dalman, 1820

Entedon costalis Dalman, 1820: 174 .

Tranocera costalis Curtis, 1829: 116 (new combination for Entedon costalis ).

Eulophus discolor Nees, 1834: 172 .

Elachestus costalis (Dalman) , Nees, 1834: 143.

Pleuropachus costalis (Dalman) , Westwood, 1837: 436 (new combination for Entedon costalis ).

Eulophus martialis Förster, 1841: 42 .

Eulophus discolor Nees, Dalla Torre, 1898: 29 (possible synonym of Pleuropachus costalis ).

Eulophus martialis, Dalla Torre, 1898: 29 (new synonym of Pleuropachus costalis ).

Entedon costalis punctatus Erdös, 1944: 18 .

Type material. Lectotype ♂ ( Fig. 1A, B ) and paralectotype ♂ (both on the same pin), Sweden ( Naturhistoriska Riksmuseet , Stockholm, Sweden).

Additional material: 2 ♀, 3 ♂, Kyiv, Park Druzhby Narodiv (plot 4, Table 1), 24.vi.1995, swept from Taraxacum officinalis agg., inflorescence ; 1 ♀, 2 ♂, 06.vi.2006, Kiev, “ Solomyanka ” (plot 5, Table 1), ex earthen cells of G. punctiger ; 7 ♀, 7 ♂, Kiev, Lysa Hora (plot 3, Table 1), ex earthen cells of G. punctiger , 9–14.v.2006 ( Schmalhausen Institute of Zoology of Ukrainian Academy of Sciences, Kiev, Ukraine) ; 1 ♀, 3 ♂, Danemark, 16/5 97 [“ Tekkekjib ” handwritten], coll. Schlick ; 6 ♀, 9 ♂, ibid .; 1 ♂, 18/5 90, ibid .?; 1 ♂, 2 ♀, 12/5 95, ibid .; 1♂, 9/5 86, ibid .?; 2 ♂, 13/5 92, ibid .?; 4 ♀, 22/5 86, ibid .?; 1 ♀, 18/5 90, ibid .?; 4 ♂, 16/5 97, ibid. (collection of the Zoological Museum , University of Copenhagen, Danmark) ; many non-accounted specimens in the collections of Természettudomanyi Museum Allatara (Budapest, Hungary), and the Natural History Museum (London, UK) .

Recent literature. Entedon costalis has gained little attention since its description ( Dalman 1820). Apart from some regional records ( Erdös 1944; Graham 1963; 1971), this species was mentioned in comparative diagnosis of E. marginalis , which is similar in structure of fore wing of male ( Askew et al. 2001).

Comparative notes. Within the European fauna, males of E. costalis are easily recognizable in having notably expanded marginal vein ( Fig. 1C, D ). In this respect E. costalis resembles E. marginalis , but the males differ in the structure of antennae ( Askew et al. 2001). Females also possess the expanded marginal vein, which distinguishes them from the females of most other species. Females of E. costalis and E. marginalis differ mostly by size (about 3.5 mm in E. costalis , and about 1.9 mm in E. marginalis ). In all morphological aspects females of E. costalis resemble females of E. pseudonigritarsis Erdös , from which it barely differs, except the marginal vein is broadened throughout in E. costalis and lower margin of clypeus is more notably produced in E. pseudonigritarsis . Males of E. pseudonigritarsis are distinctly different from males of E. costalis in having notably narrower marginal vein (not so distinctly thickened as in E. costalis ). Apart from these morphological differences, E. pseudonigritarsis is a good biological species, having a different host (a weevil Coryssomerus capucinus (Beck 1817) on scentless chamomile Tripleurospermum perforatum, Hinz & Müller-Scharer 2000 ).

Distribution. Austria, Switzerland, former Czechoslovakia, former Yugoslavia ( Bouček & Askew 1968); Croatia, Norway ( Bouček 1977), Czech Republic, Slovakia ( Kalina 1989); Germany ( Förster 1841, Nees 1834, Vidal 2001); Hungary ( Erdös 1944, 1956); Russia ( Yefremova 2002); Sweden ( Dalman 1820, Hansson 1991), Ukraine (new record).

Biology. Egg-larval parasite of dandelion weevil Glocianus punctiger .

Ecology. The host. Glocianus punctiger ( Fig. 6A ) is one of only a few weevils attacking dandelions in Europe (Scherf 1963, Honĕk et al. 2005, Honĕk & Martinková 2005). This weevil was established in biocontrol programs against dandelions in North America ( McAvoy et al. 1983). Likewise many ceutorhynchine weevils, Glocianus punctiger has underground life span; the biology of the weevil is described below in order to facilitate understanding of the parasitoid-host relationships of Entedon costalis .

Females of G. punctiger oviposit in April and May, in synchrony with flowering of dandelions. The female weevil lays its eggs into the dandelion flowerstalk, through a hole cut by the female’s mandibles. Oviposition sites are traced by brown drops of oxidized sap released as a result of damage caused by the female weevil. The eggs are deposited on the internal surface of the flowerstalk ( Fig. 6B ) and are either not attached and simply adhered to the moistured inner flowerstalk surface, or glued there by the hardened plant's sap ( Fig. 6B ).

The egg is about 0.8 mm long and 0.5–0.6 mm wide, ovoid ( Fig. 6C ), but occasionally conical ( Fig. 6D ). The embryo develops within about 3–4 days. The newly hatched first instar is pale-yellow, its head capsule is about 0.9–1.0 mm long, pale, but darkens soon. The head capsule of the first instar larva is darker than the head capsules of the older instars. Upon eclosion, the first instar crawls upwards to the receptacle ( Figs 6E, F ). It begins the consuming the receptacle and molts to the second instar. These instars are found in the prereceptacle cavity, within the receptacle plate, or among the young seeds. The larva consumes young seeds, and moults to the third (final) instar shortly before maturation of the seeds. As soon as the mature seeds disperse the mature larvae are revealed, fall to the ground and quickly bury into the soil. There they prepare an ovoid earthen cell, about 3.0 mm long, pupating therein about one week later ( Fig. 14C, D ). In Kiev, the mature larvae of G. punctiger drop out from the seed heads of dandelion from early May through early June, leaving darkened orifices indicating their injuries to the host plant. Pupae can be found in earthen cells about 5–8 days after larvae fall to the ground, and adult beetles emerge about two weeks later (early to late June). Emerged beetles feed on dandelion rosettes during rest of summer and overwinter in the soil. Honek et al. (2005) reported that larvae of this weevil were found in Czech Republic until September, associated with continual flowering of dandelions in some patches.

Ovipositing behaviour of E. costalis . The females of E. costalis can be found in the field in the north of Ukraine (Kiev) for a very short time, from late April until mid May. The parasitoid female searches along the dandelion flowerstalk by drumming its surface with her antennae. It is very likely that she locates the host by the hardened host-plant sap ( Figs 4A, B , arrowed), in places of penetration of the weevil’s rostrum. Once the female has located a hardened sap, she starts more frequent drumming and soon afterwards starts probing the flowerstalk by her ovipositor ( Fig. 4A, C ). She bends her gaster downwards, briefly hooks the ovipositor saw into the plant tissues and then releases the gaster so that it strengthens in a position perpendicular to the ovipositor. Thereafter she penetrates the flowerstalk wall and presses the gaster downwards up to the plant surface ( Fig. 4B, D ). During this time she moves the ovipositor inside the flowerstalk and probably searches for the host egg inside. If the egg is not found, or occasionally by some other reason, she withdraws the ovipositor from the host egg and continues searching. The probing normally lasts 8–15 seconds. If the egg is found, the ovipositing starts. The female moves like in process of probing, but keeps the ovipositor more deeply inside the flowerstalk, in average about 45–50 seconds. During all this time the female carries out rhythmic, twisting movements of her gaster ( Fig. 4D ). Results

Figures

FIGURE 1. Entedon costalis: A, B. Pinned male lectotype: A. Habitus, B. Fore wing; C, D. Fore wings of reared specimens: C. Female, D. Male.

FIGURE 4. The female of E. costalis on dandelion flowerstalk: A, B. Female probes through the wall of the flowerstalk; C, D. Oviposition of the same female; white arrow, hardened and oxidized dandelion sap in the place of the oviposition hole made by the host weevil female.

FIGURE 6. A–F. Glocianus punctiger. A. Adult; B. Eggs within dandelion's flowerstalk; C, D. Eggs under light microscopy. E, F. First instar feeding on young seeds.

FIGURE 14. E. costalis, final instar: A. Habitus; B. Mouthparts; C, D. Earthen cells of G. punctiger: C. Intact, D. Partly dissected with the weevil larva visible; E. Final instar of E. costalis with shriveled host remnants behind, isolated from the host earthen cell; F, pupa of E. costalis; grey arrows, abdominal spiracles; black arrow, thoracic spiracle.