Coniceromyia Borgmeier, 1923

Coniceromyia Borgmeier View in CoL (total of 10 photos of three mating events examined: Figure 2 View Figure 2 )

Coniceromyia View in CoL is among the phorid genera with the most diverse secondary sexual characteristics ( Ament et al. 2021). The males of this genus have sexually dimorphic structures in different podomeres of all legs, wings and head. The male forelegs are highly modified and diverse, with the foremetatarsus being unique for most species of the genus (figs 8–12 in Ament et al. 2020). The evolution and functional morphology of these structures were discussed by Ament et al. (2021) but without any direct evidence of their use. The photos we examined here are the first records of Coniceromyia View in CoL mating and bring light to the possible function of some of these structures.

Coniceromyia View in CoL has a mating position unique in the family, with the male projected anteriorly, sometimes with his head even farther anterior than the female’s ( Figure 2A–D View Figure 2 ). This is possible due to the male being slightly larger than the female and the female abdomen bending upward during mating. The position allows the male to suspend its forelegs over the female’s head, in one photo even touching the female’s frons ( Figure 2D View Figure 2 ). Coniceromyia View in CoL males have several sexually dimorphic features on the foreleg which could be in use in this position. In general, the male structures do not appear to be physically restraining the females; instead, they seem to be used as stimulatory contact devices, possibly contacting the frons or arista of the females (although a clear contact is only visible in Figure 2D View Figure 2 ).

Some of the main sexually dimorphic features of Coniceromyia are present in the male foremetatarsus ( Ament et al. 2021). The males of all species have an apical anterodorsal setulose projection in this podomere (visible in Figure 2E View Figure 2 ) which is often accompanied by a highly variable anterior excavation. Often, the foremetatarsus is also swollen or elongated and in some species has complex microsculpture in its excavation. These characteristics alongside the position of this tarsomere in the photos indicate that the males could be using the foremetatarsus to mechanically stimulate the females. Additionally, the morphological modifications of the foremetatarsus suggest the possibility of internal glands, which, in this case, could be producing secretions used in this stimulation.

Some other male features are also corroborated as potential female stimulatory structures by their morphology and the mating position of the photos. This is the case for males’ elongated, ventrally curved setae on the apical foretarsomere, a ventral setulose process on the foretrochanter and elongated setae ventrally on the midcoxa (present in one, six and one species, respectively; Ament et al. 2021). All of these features would be able to contact the female in this male-forward position. Other male-exclusive features also seem suited for mechanical stimulation, such as the curved forecoxa of one species and the strong setulae, spines and microsculputural modifications of the foretibia and forefemur of others ( Ament et al. 2021). However,none of these podomeres appear in the photos with a potential contact with the female.

Figure 2F View Figure 2 shows an aggregation of Coniceromyia males over a leaf. This could represent the first non-aerial lekking behaviour recorded for the phorids (although some other forms of aggregation should be also considered). A lekking behaviour in the genus could be related to some other sexually dimorphic features of Coniceromyia that suggest a visual courtship function such as species-specific wing and foreleg patterning.

The photos are not helpful in providing insights on the role of some other male exclusive characteristics such as the enlarged first flagellomere present in most species and the hind femur posterior group of tiny blunt setulae near the base (figs 17–23 in Ament et al. 2020). In contrast to Dohrniphora , which have setulae and ornamentation in the same position on the hind femur (discussed below), the photos do not show Coniceromyia males contacting the females with their hind femur. Additionally, the hind femur group of tiny blunt setulae of Coniceromyia are much less complex and diversified than Dohrniphora .