Pollinating fig wasps (Hymenoptera, Agaonidae) are obligate mutualists with their Ficus (Fig tree) hosts, but they are outnumbered by a diverse group of non-pollinating fig wasps (NPFW) that also develop within figs. Pollinating fig wasps have been studied extensively, whereas much less is known about the biology of NPFW.

Under the guidance of Prof. YANG Darong, XTBG PhD candidate WANG Zhenji investigated the reproductive strategies of Walkerella sp.1 associated with Ficus curtipes and Walkerella sp.2 associated with Ficus benjamina. Their experimental studies proved that these two Walkerella species are gall formers. Walkerella sp.1 was the first fig wasp species to oviposit on F. curtipes. The larvae of Walkerella sp.1 were only found in the most external ovary layer of the fig. Walkerella sp.2 starts ovipositing after several other NPFW have already laid their eggs in F. benjamina. The progeny of Walkerella sp.2 are distributed in the external ovary layer, the middle ovary layer, and/or the inner ovary layer of the figs. Their data also suggested the sex ratios of Walkerella sp.1 and Walkerella sp.2 were female-biased in either manipulated figs or in natural figs.

WANG Zhenji and YANG Darong also found that Walkerella sp. from F. benjamina has dark and pale wingless males. Their observations and field experiments in Xishuangbanna, SW China suggested that the sex ratio of Walkerella sp. did not vary with foundress number or brood size. The frequency of dark males increased with brood size and foundress number and they were absent from figs with a single foundress. This produced a higher proportion of dark males at higher densities. They also found that males of both morphs fought, but injuries to dark males were more frequent. Dark males were more likely to disperse away from their natal figs and they were more resistant to dehydration.