Bittacus

Machado, Renato Jose Pires, Godoi, Fabio Siqueira P. & Rafael, José Albertino, 2009, Neotropical Mecoptera (Insecta): New generic synonymies, new combinations, key to families and genera, and checklist of species, Zootaxa 2148, pp. 27-38 : 28-29

Bittacus and Thyridates

The genus Bittacus was created for the European species, B. italicus (Müller, 1766) (= B. tipularia (Fabricius, 1775) . Subsequent to that, the first New World species, B. stigmaterus Say, 1823 , was described. Nowadays Bittacus is the most diverse genus of Bittacidae , with species in all biogeographical regions.

Navás (1908) proposed the creation of the genus Thyridates for Bittacus chilensis Klug, 1838 , but Esben- Petersen (1921) considered the differentiating characters proposed by Navás inconsistent and synonymized Thyridates with Bittacus , which was accepted by subsequent authors ( Byers 1972; Penny 1975; Penny & Byers 1979a, b).

The synonymy between Thyridates and Bittacus was questioned by Willmann (1983), who proposed the revalidation of Thyridates and transferred 12 species from Bittacus to it. This author pointed out two characters to support the group: the origin of Rs1+2 forming nearly a right angle and extra costal crossveins present beyond the humeral crossvein. In the same paper the author also used a biogeographical discussion to support his hypothesis, pointing out that Bittacus is broadly distributed in Eurasia and North America (Laurasian distribution) but does not occur in the Australian region, and thus, Bittacus cannot be the predominant genus of Bittacidae in South America.

Collucci and Amorim (2000, 2001) adopted Willmann’s classification, described four new species of Thyridates , and transferred another three species from Bittacus to Thyridates . These authors pointed out that Bittacus is probably Holarctic, while Thyridates is a Neotropical genus. They also proposed another five synapomorphies to emphasize the consistency of the group: fork of Rs more basal than the apex of Sc; crossvein sc-r apical; thyridium evident; pterostigma elongate; and species relatively large.

Petrulevičius (2003) reiterated the consistency of Thyridates and discussed the characters introduced by Willmann (1983) and Collucci and Amorim (2000). The author considered two of the characters as least problematic: origin of Rs1+2 making nearly a right angle as proposed by Willmann (1983), and elongated pterostigma as proposed by Collucci and Amorim (2000); he emphasized that the strongest character was the presence of two or three pterostigmal crossveins, which distinguish an elongated pterostigma ( Fig. 1 ). In addition to these two characters Petrulevičius (2003) also proposed one more: presence of a forked Kreuz der Bittaciden (bifurcations of veins Rs3+4, M1+2 and M3+4, arising at the same level, where the bifurcation in M1+2 becomes more basal, almost at the same level as crossveins rs4-m1+2 and m1+2-m3+4). Based on these three characters the author described a fossil species from Argentina ( Thyridates novokschonovi Petrulevičius, 2003 ) and transferred seven African species from Bittacus to Thyridates , thus expanding the geographical distribution of Thyridates . He suggested a Gondwanan origin for the group, before it became restricted to the Neotropical region.

Although these authors considered Thyridates a valid genus and introduced some putative synapomorphies, other authors have ignored these works and have not accepted Thyridates ( Byers 1996, 2004; Byers & Roggero 1992), which has caused nomenclatural instability.

For the development of this work we have examined specimens of 25 species (see examined specimens below) from the New World, mainly to analyze the three characters pointed out by Petrulevičius (2003). The first one, the origin of Rs1+2 at nearly a right angle, is the most constant character state among the South American species now classified in Thyridates . However, this character state is not present in all species from South America and Africa ( Petrulevičius 2003) and also can be found in some Nearctic species of Bittacus , such as B. chlorostigma MacLachlan, 1881 , B. occidentis Walker, 1853 , B. pilicornis Westwood, 1846 , B. punctiger Westwood, 1846 , and B. stigmaterus Say, 1823 . The second character state, an elongate pterostigma with two or three crossveins, is also variable. Bittacus maculosus Byers, 1965 , B. diversinervis Souza Lopes & Mangabeira, 1942 , B. pintoi Souza Lopes & Mangabeira, 1942 , and B. femoralis Klug, 1838 contain specimens with only one crossvein and sometimes with one crossvein on one side of the body and two or three on the other side. Other genera, such as Pazius and Kalobittacus , also share this character state. The third character, the presence of a forked Kreuz der Bittaciden, occurs practically in all species of Thyridates and Bittacus that we have examined, but in the majority of them the bifurcation M1+2 is a little more apical than the others, and does not reach the level of crossveins rs4-m1+2 and m1+2 -m3+4, the opposite of what Petrulevičius (2003) indicated and exactly the same as occurs in some Kalobittacus species.

The biogeographical discussion in Willmann (1983) was strongly based on the absence of Bittacus in the Australian region to explain why Bittacus could not occur in the Neotropical region. However this conclusion no longer can be considered valid as Lambkin (1988) has described the first Australian Bittacus ( B. eremus Lambkin, 1988 ).

The Andes Mountains is one of the most formidable biogeographical barriers for insects in South America. The mecopteran fauna in the lowlands west of the Andes is almost completely different than that east of the Andes; only Bittacus occurs in both regions, but with just a single species, B. chilensis , on the west side. This species, the basis for Thyridates ( Navás, 1908) , has some peculiar characteristics, such as the large body size and large eleventh tergite. When a comprehensive phylogenetic study related to all of these taxa is done we may have to reconsider resurrection of Thyridates , but only for this particular species, not for the others.

Because of the inconsistency of the three characters discussed we opt to not accept Thyridates as a valid genus, as Esben-Petersen had concluded in 1921. Thus, we transfer to Bittacus all species recently described in Thyridates : Bittacus brunnipenis ( Collucci & Amorim, 2000) n. comb., B. froehlichi ( Collucci & Amorim, 2000) n. comb., B. latreillei ( Collucci & Amorim, 2000) n. comb., B. novokschonovi ( Petrulevičius, 2003) n. comb. and B. willmanni ( Collucci & Amorim, 2001) n. comb.. As Thyridates is again synonymized with Bittacus all of the African species that Petrulevičius transferred to Thyridates must again be treated in Bittacus : B. chevalieri Navás, 1908 , B. erythrostigma Byers, 1975 , B. nebulosus Klug, 1838 , B. oreinus Navás, 1914 , B. stanleyi Byers, 1968 , B. testaceous Klug, 1838 , and B. weelei Esben-Petersen, 1913 .

Figures

FIGURE 1. Fore wing of Bittacus chilensis. A = anal vein; C = costal vein; Cu = cubital vein; h = humeral crossvein; M = medial vein; R = radial vein.