Strepsiptera are entomophagous endoparasites that stylopize seven orders of Insecta and is one of the least species-rich taxa among insect parasitoids. This order consists of 14 families, and their known hosts are distributed across 36 families in seven orders of Insecta (1, 2). The Strepsiptera biodiversity recorded include 603 species of Strepsiptera described worldwide (1, 2). In Brazil, 33 Strepsiptera have been recorded so far (3); however, many more remain undescribed. The strepsipteran family Myrmecolacidae Saunders, 1872, exhibits sexually dimorphic host relationships known as heterotrophic heteronomy, where males stylopize Formicidae Latreille, 1802 (ants), and females stylopize Orthoptera (crickets, grasshoppers) and Mantodea (mantids) (1, 2, 4–6). Heterotrophic heteronomy [sensu Walter (7)] is an unusual form of polymorphism and is rare not only in Strepsiptera but also in insect parasitoids in general. This phenomenon occurs convergently in two lineages of sexually dimorphic parasitic insects: the Myrmecolacidae (Strepsiptera) and the Aphelinidae Thomson, 1876 (Hymenoptera, Chalcidoidea).

Males are matched to conspecific females by molecular characterization, and so far, only two species have been unequivocally matched (5, 6). Majority of the Myrmecolacidae described (approximately 93 so far) consist of free-living males that have been found in traps. However, only hosts of 23 species (from nine genera of six subfamilies) stylopize ant hosts (2), which is approximately a quarter of the total male Myrmecolacidae described. This is curious as ants comprise the largest group of invertebrates in any habitat, yet stylopized ants are seldom encountered (8).

Looking for stylopization by males of Myrmecolacidae, the entire contents of ant nests have been examined; however, these attempts have been largely unsuccessful Kathirithamby personal observation. In addition, Ogloblin (9), then Kathirithamby et al. (6) and Nakase et al. (10), observed changes in the behavior of positive phototropism and elevation in stylopized ants, which are hypothesized to be mediated by parasites (11).

It is speculated that, when ants are stylopized, they remain in the nest even after the extrusion of the male cephalotheca, while the male strepsipteran undergoes pupation (within the nest) (2). The cephalotheca of the male strepsipteran is the cap of the puparium that extrudes from the host. It generally has the same coloration as the ant’s cuticle, which may act as a camouflage (2). As far as is known, stylopized ants in the nests are not attacked by mates; however, if they were to be active outside the nest, they would be prone to predation (8). Just before the male myrmecolacid emerges, the ant leaves the nest, climbs to a high point on vegetation, and, at this vantage point, the free-living male strepsipteran emerges from the puparium. After this, the ant with its empty puparium, which is susceptible to a fungal infection, dies (Kathirithamby, personal observation).

The ants of the genus Ectatomma Smith, 1858 (Formicidae: Ectatomminae), are opportunistic omnivores, primarily functioning as generalist predators. They inhabit subterraneous nests with a medium population density (~50–200 inhabitants) and forage on the ground (12). Here, we document a new host record of the stylopization of a worker of the ant Ectatomma edentatum Roger, 1893, by male Myrmecolacidae (Strepsiptera).

Sampling was conducted in an urban fragment of Atlantic Forest in the city of Salvador, Bahia State, in the northeast region of Brazil (12°57′ S, 38°26′ W). Specimens were collected using 16 yellow pan traps (dishes with a maximum diameter of 21.5 cm, an internal diameter of 17 cm, and a depth of 3 cm) at ground level with a distance between them of 30–50 cm, between October 8 and 12, 2025. The trays were filled with 10%–20% aqueous solution of commercial NaCl and 1 mL of commercial neutral detergent per liter solution. A Leica MZ125 stereomicroscope with an attached Leica Flexacam C5 camera (Leica Microsystems, Wetzlar, Germany) was used to capture images of the specimens. The illustration was created using Adobe Illustrator 2025 software. Host and parasitoid identification was performed based on the identification keys (13–15) for Neotropical entomofauna and with the assistance of specialists (J.H.C. Delabie and J. Kathirithamby, respectively). The specimen obtained was deposited in the entomological collection of the Natural History Museum of the Federal University of Bahia (MHNBA-UFBA, Salvador, Brazil).

One stylopized worker specimen of the ant E. edentatum (Formicidae: Ectatomminae) was collected (ID no. MZUFBA 00461).

The ant that was collected contained an empty male puparium with a hinged cephalotheca (Figures 1A–C), which represents the first host record of stylopization of the species E. edentatum (Formicidae: Ectatomminae). Although the free-living male strepsipteran had emerged, the cap of the puparium, the cephalotheca, remained hinged to the host ant.

Stylopized ants with a hinged cephalotheca have also been reported for Pheidole sp. (Myrmicinae) stylopized by the male puparium of Caenocholax sp. (Strepsiptera: Myrmecolacidae) from Tapachula, Chiapas, Mexico (15); a minor worker of Pheidole sp. (Myrmicinae) stylopized by the male puparium of Stichotrema robertsoni Kathirithamby, 1991 (16) (Strepsiptera: Myrmecolacidae), from Natal, South Africa; and an alate Myrmelachista zeledoni Emery, 1896 (Formicinae), stylopized by the male puparium of Caenocholax sp. from Puntarenas Province, Wilson Botanic Gardens, Costa Rica (17). The reason for the hinged cephalothecae remains unknown.

Emerging strepsipteran males have been observed breaking the cap at the “line of weakness” [sensu Kathirithamby et al. (18)] of the puparium of Elenchus tenuicornis (Kirby, 1815) (Strepsiptera: Elenchidae) with an analogous structure, similar to the ptilinum of Diptera (19), or by employing their mandibles, as seen in Xenos peckii Kirby, 1813 (Strepsiptera: Xenidae) (20). In both instances, the cephalotheca completely detaches from the puparium, along its “line of weakness.” The mechanism the male Myrmecolacidae uses to “cut” along the “line of weakness” remains unknown; however, this line might not be circular, as in other Strepsiptera, which could allow the cap to remain hinged to the ant host after the emergence of the male strepsipteran.

Finding a stylopized ant in a yellow pan trap is a result that deserves attention. As previously reported, stylopized ants do not usually leave the nests until the free-living males are ready to emerge from their cephalothecae (1, 2). This makes their collection difficult through passive sampling and makes our result unprecedented for sampling stylopized ants since their collection commonly occurs through active field collection or captive rearing (1, 2, 6, 10) methods with higher costs and sampling effort. Considering this information, we propose two possible hypotheses to explain our unprecedented results. In the first hypothesis, the ant would have accidentally fallen from the vegetation above into the traps after dying from fungal infection, as this type of infection tends to kill the hosts relatively quickly after the male emerges (1, 2). However, the time period in which the ant is infected by fungi resulting in its death is still unknown. Thus, a second hypothesis for our results would be that the stylopized ant was attracted to the yellow pan trap before the infection became fatal to the ant. This latter hypothesis is corroborated by the fact that non-stylopized ants of the species E. edentatum are frequently collected in these traps (André L. Marambaia, personal observation). This shows that, even though they are terrestrial, these ants tend to be attracted to this type of trap, which can also occur with stylopized specimens.

Yellow pan traps should be considered as a collection method for Strepsiptera as they constitute a passive and low-cost method that can provide valuable results for understanding the behavior of stylopized ants, as well as the biology and the distribution of Myrmecolacidae. Yellow pan traps can therefore expand the possibility of obtaining stylopized ants in conjunction with active searching and captive rearing (6, 10), providing more data, such as those presented here. In addition, we can suggest that the combination of these methods with pitfall traps, Winkler extractors, and soil sampling tends to expand the opportunities for collecting stylopized ants since they are quite efficient in capturing ant diversity and abundance (21, 22).

This study reveals the first record of stylopization of the ant E. edentatum in yellow pan traps. As the male of the Myrmecolacidae family had already emerged from the host ant, no molecular study was performed. However, future collections that obtain ants with prior stylopization justify conducting such studies. The study of museum material containing ants with prior stylopization is also a useful and recommended exercise. Finally, the use of yellow pan traps for collecting stylopized ants, such as those used in this study, should be considered in conjunction with other commonly used collection methods to expand collection opportunities due to its low cost and reduced sampling effort.