Megastigmus stigmatizans (Fabricus, 1798)

Nieves-Aldrey, José Luis, Nieves, Maria Hernández & Gómez, José F., 2008, Larval morphology and biology of three European species of Megastigmus (Hymenoptera, Torymidae, Megastigminae) parasitoids of gall wasps, including a comparison with the larvae of two seed-infesting species, Zootaxa 1746, pp. 46-60 : 52

publication ID 10.5281/zenodo.181647


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Megastigmus stigmatizans (Fabricus, 1798)


Megastigmus stigmatizans (Fabricus, 1798)

Measurements: ex A. kollari (n= 7), body length: 1.7–2.9 (2.3) mm; maximum width: 0.9–1.5 (1.3) mm; ex A. quercustozae (n= 1; measured specimen without mean information), Body length: 5 mm; maximum width: 3.1 mm.

Similar to the larva of M. dorsalis in general appearance and most morphological characters, but differs in the following ways:

Larger size. Body slightly wider at the mid-region and tapers more abruptly posteriorly ( Fig. 1 View FIGURE 1 D; Fig. 6 View FIGURE 6. A E). Truncate incised anterior margin of vertex prolonged into a relatively wide medial groove, which is as wide as the frontal pit ( Fig. 3 View FIGURE 3 D). Frontal pit rounded ( Fig. 6 View FIGURE 6. A F). Antenna situated far to the anterior margin of medial frontal pit; antennal setae situated at a mid-distance between the medial frontal pit and the antennae, clearly above the antennae and below the median frontal pit. Antero-medial setae of the antennal area long (length is half of the distance between antennae) and the latero-clypeal seta are 0.5 × as long as width of labrum. Mandibles large, heavily sclerotized; left mandible has five teeth ( Fig. 5 View FIGURE 5 G) while the right mandible with four teeth ( Fig. 5 View FIGURE 5 H); first tooth acute, more than twice as long as second; apex of second and third teeth blunt; fourth tooth has a rounded apex; third and fourth teeth widely separated, with the separation being as wide as the width of fifth tooth.

Biology: Megastigmus stigmatizans is a polyphagous parasitoid of cynipid galls on oaks of the section Quercus . It is associated mainly with large lignified galls of agamic generations of Andricus species ( Askew 1966, Nieves-Aldrey 1984). We have observed that the larvae of M. stigmatizans attack the larva of A. kollari occupying the central cell of unilocular galls ( Fig. 6 View FIGURE 6. A G). This is in contrast to the closely related species M. dorsalis which attacks Synergus umbraculus occupying secondary cells in the gall tissue.

Materials examined. ex A. kollari , on Quercus faginea : Spain, Madrid: Dehesa de Arganda (20 /iv/05) (n= 4); on Q. pyrenaica: El Escorial (2 /vii/03) (n= 3); ex A. quercustozae , on Q. faginea : Spain, Ciudad Real: Puerto de Despeñaperros (15 /x/04) (n= 1). JLN-A leg.