Balduf (1935) lists _Ripidius boissyi_ as parasitic on nymphs of _Ectobius pallidus_ giving Abeille de Perrin (1909) as a source for this information. However, Abeille de Perrin simply presumed that _R. boissyi_ parasitized _E. pallidus_ because he collected this cockroach in the same habitat as the beetle. Abeille de Perrin suggested that the species of the genus _Ripidius_ lived in the bodies of cockroaches, but there are no rearing records, as far as we know, of _R. boissyi_ from cockroach hosts.
Chobaut (1919), in France, collected both _R. denisi_ and _Ectobius pallidus_ when beating an oak tree. Because of the known association of other species of _Ripidius_ with cockroaches, he presumed that this beetle was parasitic on _E. pallidus_, a cockroach common in this beetle's habitat.
_Synonymy._--_Symbius blattarum_ Sundevall [Leng, 1920].
_Natural hosts._--_Blattella germanica_, on shipboard (Sundevall, 1831); Germany (Aclogue and Fowler, _in_ Burr, 1899a); on steamship "Samui" (Stamm, 1936); on cruiser "Duguay-Trouin" (Barbier, 1947); Hawaii (Williams, 1946a): This last record was based on a specimen dissected from an adult German cockroach collected on an airplane from the South Pacific. The parasite was reported as _Ripidius_ sp. by Williams, but Weber (1948) made the specific identification.
_Ectobius pallidus_? Abeille de Perrin (1909) stated that _R. pectinicornis_ was first described by Sunders [sic] as _blattarum_ because it had been captured in the body of _Ectobia livida_. We presume that Abeille de Perrin was referring to Sundevall's work in which the host was given as _Blattella germanica_.
_Periplaneta americana_, on shipboard (Sundevall, 1831): One nymph only.
With the exception of the single nymph of _P. americana_, _R. pectinicornis_ apparently attacks only adult females and nymphs of _B. germanica_. Barbier (1947) found only _B. germanica_ parasitized, although both _Blatta orientalis_ and _Supella supellectilium_ were prevalent on board the ship. Primary larvae of the parasite failed to parasitize _Supella_.
_Adult behavior._--The winged male is relatively active compared to the apterous female; it runs around, flies well, and jumps on the female when in her vicinity. The female remains stationary and lays eggs around her by bending her long ovipositor (Sundevall, 1831). The eggs (50-100) are laid among a network of silk fibers secreted by the female. The female dies after completing oviposition (Barbier, 1947).