Megaselia scalaris (Loew, 1866)

Megaselia scalaris (Loew, 1866) View in CoL

( Figs. 1A, B View Figure 1 ),

recorded for the first time in Minas Gerais, was found in five species of social wasps, all records of new associations, with emphasis on a new host genus ( Tab. 1 View Table 1 ).

Megaselia scalaris (Loew, 1866) is a cosmopolitan species, capable of exploring different types of resources in the environment, where they can be detritivores, predators, parasitoids or facultative parasites ( Disney 2008). There are records of M. scalaris in colonies of various social Hymenoptera such as Apis mellifera Linnaeus, 1758 ( Santini 1998), army ants ( Disney & Berghoff 2005), and in social wasps: Leipomeles dorsata (Fabricius, 1804) ( Disney 1994) , Polybia jurinei Saussure, 1854 and Mischocyttarus cassununga (R. von Ihering, 1903) ( Somavilla et al. 2015) , in addition to records on insects from other orders (see a small review at El-Hawagry et al. 2021). Due to the great behavioral and feeding plasticity of M. scalaris and the great diversity of resources available in the colony, it was not possible to determine what role it played in social wasp colonies, however, very likely M. scalaris acted as a parasitoid of larvae and pupae and as detritivore. A second species of Megaselia was registered in a colony of Apoica pallens (Fabricius, 1804) . An individual of Metopininae was recorded in a colony of Mischocyttarus drewseni de Saussure, 1857 , however, as it is a male in poor condition, it was not possible to carry out a generic identification.

The Stratiomyidae family were represented by two species, each in a wasp species. Both records are the first occurrences for the social wasp species. Hermetia illucens (Linnaeus, 1758) in colonies of social bees, with or without stingers, has been documented in North America ( Riley & Howard 1889; Auth et al. 2021, both in the United States of America), South America ( Copello 1926, Argentina) and, more recently, in Southeast Asia ( Ivorra et al. 2020, Malaysia). Some other records point to the presence of Hermetia larvae in bee nests, however, there is no indication of which species ( Borgmeier 1930; Rau 1933; Nogueira-Neto 1997; Devanesan et al. 2003). Hermetia illucens larvae develop in a wide variety of organic matter, mostly at some stage of decomposition, from manure and meat to fruits, vegetables, wood, as well as fungi and bacteria (Tomberlin et al. 2002; Gobbi 2012; Soares et al. 2020), so that the records of Hermetia in bee colonies are attributed to the poor maintenance conditions of the colonies themselves, many of which have already been damaged by some other cause. Although the species is present in social insect colonies, none of the species has been reported as an obligate host so far and the immatures of H. illucens likely take advantage of the damaged and abandoned state of the colony ( Ivorra et al. 2020).

The present record corroborates this hypothesis since it occurred in a nest of A. vicina in the phase of abandonment, which was nested inside a termite mound. In this phase, only newly emerged adults remain in the colony, which causes a lack of maintenance and a consequent deterioration of the nest with the subsequent decomposition of the combs and the immature ones dying. Thus, it is believed that the immatures of H. illucens were, likewise, attracted to the colony by the decomposing material, rather than being a parasitoid of immature wasps. This is the first record of H. illucens in wasp nests.

In addition to the records of Hermetia ( H. illucens and H. fenestrata de Meijere, 1904 ), only Sargus flavilatus James, 1973 has been reported infesting social Hymenoptera ( Genaro 1996, as Sargus lateralis Macquart, 1834 ), in colonies of Mischocyttarus cubensis (de Saussure, 1854) , collected in Cuba. Here we also report the registration of Sargus fasciatus Fabricius, 1805 ( Figs. 1C, D View Figure 1 ) in a newly abandoned nest of Polistes simillimus Zikán, 1950 . Immatures of Sargus Fabricius, 1798 are also associated with decaying organic matter ( McFadden 1967) and, quite possibly, in the same way as commenting above to H. illucens , Sargus larvae can thus taking advantage of the colony’s deteriorating condition.

Only one species of Ulidiidae has been recorded, Acrosticta apicalis (Williston, 1896) ( Figs. 1E, F View Figure 1 ), registered for the first time for Brazil. It was found only in an abandoned nest of Mischocyttarus cassununga (R. von Ihering, 1903) , an independent foundation wasp. Nothing is known about the biology of this species, but Lipsanini species with known biology are mostly associated with monocots (cereals and palms), living in tissues damaged by other insects and young inflorescences, with some genera such as Euxesta Loew, 1868 being important pests of cereals such as maize ( Kameneva & Korneyev 2010). It is possible that A. apicalis was feeding on decomposing organic matter present inside the nest.

Chloropidae were also represented by only one species. Pseudogaurax aff. longilineatus Sabrosky, 1949 ( Figs. 1G, H View Figure 1 ), the first time recorded for the state of Minas Gerais, obtained from an abandoned nest of Polistes melanosoma de Saussure, 1853 . Pseudogaurax Malloch, 1915 is a poorly studied genus, which still needs a recent revision, and what is known about the feeding behavior is that it contains species with larvae that prey on eggs and larvae, attacking mainly spider ovisacs, Mantodea oothecae and Megaloptera egg mass, and ant larvae ( Sabrosky 1989; González et al. 2016; Melo & Wheeler 2009). A recently abandoned social wasp nest still has eggs, larvae and pupae, however, the adults no longer protect and care for the nest. In particular, independent foundation wasps, such as Polistes , do not have a protective envelope, that is, the comb and cells are exposed. Thus, egg predators like P. aff. longilineatus , has free and easy access to eggs abandoned in the colony, which could potentially explain the presence of this species of fly.

Understanding the ecological relationships between groups of insects provides subsidies for studies of ecology, biology, and behavior of the organisms involved in order to develop conservation strategies not only for the organisms but also for the areas where they occur.