Strepsipteran Associates

The Strepsiptera (`twisted wing parasites') are a small order of insects that spend much of their lives as entomophagous parasitoids of other insects (Kathirithamby, 1989, 2008). Females in all strepsipteran families other than the Mengenellidae spend their entire lives inside their hosts, while adult males are free-living but extremely short-lived. Only strepsipterans in the family Myrmecolacidae parasitize ants (Quevillon & Hughes, 2018).

Female strepsipterans reproduce viviparously; the first larval instars consume their mother from the inside and then emerge through her head, which protrudes from the host’s body. Following emergence, these free-living larvae then actively seek out hosts. In the case of the Myrmecolacidae, males and females exhibit sexual dimorphism in their host choice, with males parasitizing ants while females parasitize orthopterans. Having found an ant host, the male strepsipteran larvae penetrate the cuticle and once inside, go through several larval stages before pupating. This development itself does not kill the host, rather, the host must remain alive until after the strepsipterans have completed their development. When the males are ready to emerge, they leave the host via the puparium, leaving a hole in the host that often becomes colonized by fungi (Kathirithamby, 2008). Ants parasitized by strepsipterans have been observed behaving unusually (Ogloblin, 1939; Hughes, Moya-Raygoza, & Kathirithamby, 2003; Kathirithamby et al., 2010).

The very short lifespan of the free-living, adult male strepsipterans and the entirely endoparasitic lifestyles of adult female strepsipterans make recording host associations with these insects difficult. Though ants were first recorded being infected by strepsipterans by Westwood in 1861, knowledge of host records remains limited, perhaps due in part to the ant collecting methods often employed by myrmecologists (Kathirithamby & Hughes, 2002).

Known host associations between strepsipterans and ants are summarized (Kathirithamby & Hughes, 2002; Hughes et al., 2003; Cook, 2009; Kathirithamby et al., 2010; Kathirithamby, 2017). Many additional strepsipterans in genera known to infect ants have been described but have unknown host associations (see Strepsiptera database). Quevillon & Hughes (2018) report 23 records of Strepsiptera from the genera Caenocholax, Myrmecolax, and Stichotrema infecting nine ant genera.