Megastigmus pistaciae Walker, 1871

Roques, Alain, Copeland, Robert S., Soldati, Laurent, Denux, Olivier & Auger-Rozenberg, Marie-Anne, 2016, Megastigmus seed chalcids (Hymenoptera, Torymidae) radiated much more on Angiosperms than previously considered. I- Description of 8 new species from Kenya, with a key to the females of Eastern and Southern Africa, ZooKeys 585, pp. 51-124 : 101-103

Taxon classification Animalia Hymenoptera Torymidae

Megastigmus pistaciae Walker, 1871

Material examined.

3♀♀, 3♂♂, Kenya, Mount Kulal, 2.6290°S, 36.9278°E, 1640m elevation, 11 Dec 2008, ex. Pistacia lentiscus subsp. emarginata seeds, R. Copeland leg. (2♀♀, 1♂ RSC; 1♀, 1♂ ARC; 1♂ destroyed)

Male and female specimens fit the detailed description of the species by Roques and Skrzypczyńska (2003) as shown by figures 136-141 presenting the most important characteristics of female specimens from Kenya. Similarly as in most Megastigmus species developing in Anacardiaceae seeds in Kenya, males are highly variable ranging from pale forms, mostly yellow with forewing stigma without infuscation (Figures 142-144 and 146-149,) to dark forms, mostly black with infuscated stigma (Figure 145). However, the forewing description of female Megastigmus pistaciae used by Grissell and Prinsloo (2001) as a diagnostic character in the key to separate the species of Megastigmus reared from seeds of Anacardiaceae appears largely different from our observations. To separate it from female Megastigmus thomseni , Grissell and Prinsloo (2001) stated that the costal cell of the forewing of Megastigmus pistaciae presents 3 or 4 rows of setae in the apical 1/2 to 2/3 and the basal cell more than 5 setae whereas there is at most a single row of setae in the costal cell and at most 3-4 setae in the basal cell of Megastigmus thomseni . Actually, all the specimens of Megastigmus pistaciae we examined from Kenya, but also from other parts of the world (Europe, North Africa, California) did not show the characters mentioned by Grissell & Prinsloo but were closer to those attributed to the forewing of Megastigmus thomseni . Since these authors did not mention the origin of the specimens they examined, it is difficult to evaluate their observations.

In the molecular phylogeny of Megastigmus , the Kenyan specimen clusters with the other specimen of Megastigmus pistaciae from Southern Europe (Figure 14), confirming their status of sister species belonging to the same " Anacardiaceae clade". However, there was a genetic distance of 4.5% between these specimens and according to Auger-Rozenberg et al (2006) and Scheffer and Grissell (2003), clearly differentiated species of Megastigmus diverge by more than 4.0%. This suggests an opportunity to develop further studies to evaluate the possibility that the Kenyan populations represent a sibling species of Megastigmus pistaceae .

Host plants.

Pistacia lentiscus subsp. emarginata seeds.

Distribution.

Reared from samples collected in highland areas (1640-1920 m above sea level) of the Rift Valley, in northern and southwestern Kenya. Few fruits (0.6%) were infested (Table 3).

Diagnosis.

Females can be separated from those of other species with a predominantly orange colour associated with fruits of Anacardiaceae by the shape of the forewing stigma and the relative length of ovipositor. The stigma is oval in Megastigmus pistaciae (1.2 –1.3× as long as wide; Figure 141) whereas it is much more elongate in both Megastigmus transvaalensis (2.0 ×; Figure 155) and Megastigmus thomseni (1.7 ×, according to the drawing by Hussey 1956a). The ovipositor is only a bit longer than gaster length (Figure 137) whereas it is nearly twice as long as gaster in Megastigmus laventhali (1.8 ×; Figure 76) and 1.4 × as long as gaster length in Megastigmus transvaalensis (Figure 151).

The genitalia allow one to separate males from those of other species identified in seeds of Anacardiaceae . The aedeagus part above digitus is comparatively longer than in Megastigmus transvaalensis (0.8 × vs. 0.5 × as long as digitus length; Figures 148 and 162, respectively) whereas this part is much more elongated in Megastigmus hypogeus (1.2 × as long as digitus length; Figures 127, 134), Megastigmus ozoroae (1.8 ×; Figures 53, 60) and Megastigmus lanneae (1.8 ×; Figures 107, 115).