Phalacrotophora Enderlein, 1912

Ament, Danilo César & Brown, Brian Victor, 2025, Phoridae (Diptera) mating behaviour: identification of general patterns, exceptions and the use of sexually dimorphic structures based on vast citizen science data, Journal of Natural History 59 (9 - 12), pp. 739-761 : 754-756

Phalacrotophora Enderlein (total of 20 photos of

11 mating events examined: Figure 10A–H )

Phalacrotophora species may be parasites of nests of solitary bees ( Batra 1965), parasitoids of beetle prepupa or pupa ( Disney et al. 1994), parasites of Eumenidae wasps ( Borgmeier 1934) or predators of spider egg sacs ( Muma and Stone 1971). These characteristics may influence their reproductive behaviour as reproductive availability in this genus is more circumstantial, depending on limited resources (hosts or prey). Wcislo (1990) described the reproductive biology of Phalacrotophora halictorum (Melander and Brues) , a parasite of the nest of the solitary bee Lasioglossum (Dialictus) figueresi Wcislo ( Halictidae ). The mating observed by Wcislo did not include premating courtship; it did include several during-mating flights and the post-coupling behaviour of males rapidly drumming their forelegs, apparently on the female’s notum.

We analysed photos and a video of Phalacrotophora species from different localities, probably representing multiple species of the genus, and found behaviours different than the ones reported for P. halictorum . The photos show Phalacrotophora females aggregating on leaves ( Figure 10B ), possibly displaying to males ( Figure 10A ), and expanding abdominal sacs during copulation ( Figure 10C ). This eversion of abdominal sacs is probably common in the genus as many of its species have females with a tergite-free (membranous) area on their abdomen.

Most photos of mating we found for the genus showed the male in a unique perpendicular position in relation to the female, in some photos on her right side ( Figure 10F ), and in others on her left side ( Figure 10E ). A video uploaded on YouTube explained the situation: the male is constantly shifting sides during mating, a unique behaviour in the family (https://www.youtube.com/shorts/TTZaijcOVgw). We do not know of any case of similar behaviour in other insects, and it could be a behaviour of the male to twist and stimulate the female genitalia.

Figures

Figure 10. Phalacrotophora. A–B. From Donaustadt, 1220 Wien, Austria (photo credit: carnifex). C. From Iasi, Romania (photo credit: © ellas, all rights reserved). D. From Ohio, USA (photo credit: © fuzzyspider,licensed under CC BY-NC 4.0 DEED). E. From Toronto, Canada (photo credit: © brian stahls, licensed under CC BY-NC 4.0 DEED). F. From District of Columbia, USA (photo credit: Katja Schulz). G. From Dundas, Ontario, Canada (photo credit: Steve Marshall). H. From Durbanville, Cape Town, South Africa (photo credit: © Cecile Roux, licensed under CC BY-SA 4.0 DEED). Except for C and G, all photos obtained from iNaturalist (inaturalist.org/observations/), ID numbers: A–B, 84105331; D, 82485316; E, 86632821; F, 759565; H, 117471418. All photos adapted as described in the ‘Materials and methods’ section.