Em Julho de 2004, foram observados adultos de G. semirufa atacando larvas de Peckia Robineau-Desvoidy, 1830 enquanto estas se alimentavam de carcaça de porco Sus scrofa em área de cerrado. Em Dezembro do mesmo ano, no mesmo local, larvas de terceiro instar de P. trivittata foram coletadas em outra carcaça de porco e levadas ao laboratório. As larvas foram criadas em condições naturais. Das 31 pupas obtidas, emergiram 19 adultos de G. semirufa e seis adultos de P. trivittata, correspondendo a uma prevalência de 61% de parasitismo.

In July 2004, adults of G. semirufa were observed attacking maggots of Peckia Robineau-Desvoidy, 1830 while feeding on a Sus scrofa carcass in a cerrado area. In December of the same year, in the same location, third instar maggots of P. trivittata were collected from another pig carcass and taken to laboratory. They were reared in natural conditions. 19 adults of G. semirufa and six adults of P. trivittata emerged from the 31 pupae we had obtained previously, corresponding to 61% of parasitic prevalence.

The acrocerids (small headed-flies) form a small group of flies, which are difficult to find and observe. They are rare in collections. Their larvae are heteromorphic parasitoids of many families of spiders and their imagoes show a great deal of morphological variation. Little is known about the biology and systematics of this group in the Neotropical region, especially the Philopotinae. Most studies are based on species from Europe and North America. The Philopotinae occurs througout the world, and are characterized by the strongly developed postpronota, which form a shield dorsally in front of the scutum. Fifty specimens of Philopota sp. were collected from branches of Stachytarphetta cayenensis (Verbenaceae) in the Ilha da Marambaia (23º 04' S - 43º 53' W, 240 m), southern coast of Rio de Janeiro State, Brazil. The specimens were determined to Philopota n.sp. (acc. to Evert I. Schlinger). In Marambaia, S. cayenensis occurs alongside trails. Small lycosid spiders were observed associated with litter in the surrounding soil. Both males and females of Philopota n.sp. visit the flowers periodically. Couples in sexual intercourse were observed on the flowers. When feeding, they introduced their whole bodies inside the flower. A territorial behavior was observed involving both males and females. Up to four individuals were observed disputing a flower of S. cayenensis at the same time.