Eumyrmococcus corinthiacus Williams, 1993

Scupola, Antonio, Durante, Antonio, Giannuzzi, Francesco & Pellizzari, Giuseppina, 2022, The coccid-tending ant genus Acropyga Roger and its obligate associated myrmecophilous scale insect genus Eumyrmococcus Silvestri new to Italy (Hymenoptera: Formicidae; Hemiptera: Xenococcidae), Fragmenta entomologica 54 (1), pp. 89-94 : 92-93

Eumyrmococcus corinthiacus Williams, 1993

Eumyrmococcus corinthiacus belongs to the family Xenococcidae Tang, 1992 , a family of subterranean, obligate myrmecophilous mealybugs, characterized by unique morphological and biological traits.

The family is composed of 3 genera: Eumyrmococcus (20 species), Neochavesia (8 species), and Xenococcus (5 species). Their systematic position has been controversial because of their peculiar morphological and biological characteristics. For a long time, xenococcids were considered to belong to the Pseudococcidae , but they differ from pseudococcids in many morphological characters: e.g., the females do not have ducts, pores or ostioles; antennae have only 2 or 4 segments; eyes are absent; the anal ring lacks pores; the anal lobes have long setae; and the males are small, larva-like, apterous and without eyes, and the legs and antennae are strongly reduced ( Hodgson 2012; Gavrilov Zimin 2018). Moreover, the female developmental cycle of some Xenococcinae (e.g., Neochavasia species and E. smithi Silvestri ) is characterized by the presence of a quiescent pupal stage in the third instar ( Williams 1987, 2004; Kishimoto-Yamada et al. 2015) whereas in other mealybug families this is a trophic stage.

Tang (1992) erected the tribe Xenococcini for these peculiar scale insects, in the subfamily Rhizoecinae (Pseudococcidae) . Hodgson (2012), based on male morphology, concluded that Rhizoecinae mealybugs were separate from the Pseudococcidae and elevated them to family Rhizoecidae , containing two subfamilies: Rhizoecinae Williams and Xenococcinae Tang. Danzig & Gavrilov-Zimin (2014) subsequently elevated Xenococcinae to family rank ( Xenococcidae ). This position was explained in detail by Gavrilov-Zimin (2018), and the family was also recognised based on male morphology ( Hodgson 2020; Garcia Morales et al. 2016).

Eumyrmococcus females have a large head and thorax, abdomen rather tapering and, in profile, curved upwards. Eumyrmococcus species feed on the phloem of plant roots and live underground in ant-nest tunnels of Acropyga spp. ants. As discussed above, the species E. corinthiacus is associated to the ant Acropyga paleartica .

Based on the description and key by Williams (1993, 1998), Eumyrmococcus corinthiacus is easily identified by having 4-segmented antennae and 3 thick setae on each anal lobe, with 2 setae longer and stouter than the other. The longer setae each have the apical part curved, like a hook.

So far, E. corinthiacus was known only from the type locality (Perachora, Corinth, Greece). The present record of E. corinthiacus in Apulia region is the first for Italy and the second in Europe. As it is known that E. corinthiacus and the ant A. palearctica are obligate symbionts, it is likely that E. corinthiacus is also present in Greek locations where only the ant A. paleartica has been recorded so far.

Acknowledgements – We thank Gillian Watson (Natural History Museum, London) who kindly read the text and revised English language, and two anonymous referees for their valuable comments. Many thanks to Prof. Giacomo Santini (University of Florence) for his valuable advice on the study of the samples, and Gabriele Pellegrino (MSNS) for his kind help in collecting material.