Tachytes pulchrivestitus Cameron, 1908

Pulawski, Wojciech J., 2022, New Synonymy in the Afrotropical Tachytes Panzer, 1806 (Hymenoptera: Crabronidae), Proceedings of the California Academy of Sciences 67 (10), pp. 269-279 : 275-278

Tachytes pulchrivestitus Cameron

Tachytes pulchrivestitus Cameron, 1908:284 , ♀ (as pulchrivestita, incorrect original termination). Holotype: ♀, Tanzania: Tanga Region: Mombo ( NHRM), examined. Here resurrected from synonymy. – R. Turner, 1913:754 (as new synonym of Tachytes mirus ), 1917:20 (“from the description this appears to be nearest to T. rhodesiana ”).

Tachytes rhodesianus Bischoff, 1913 c:70 , ♀. Holotype: ♀, Zimbabwe: Springvale ( SAM), examined. New synonym. – R. Turner, 1917:19 (in revision of Afrotropical Tachytes , description of ♂, South Africa, Zimbabwe, as rhodesiana ); Arnold, 1923:185 (in revision of southern African Tachytes , as rhodesiana ), 1927:117 (females with six rather than five rake spines on forebasitarsus, as rhodesiana ), 1929c:389 (postocellar area incorrectly described in 1923, correctly given in description of T. midas , as rhodesiana ), 1930:4 (in checklist of Afrotropical Sphecidae ); Berland, 1942:2 ( Mali: Telimané north of Kayes; as rhodesiana ); R. Bohart and Menke, 1976:266 (in checklist of world Sphecidae ).

Tachytes midas Arnold, 1929:389, ♀, ♂. Lectotype: ♀, Zimbabwe: Bulawayo ( SAM), present designation, examined. New synonym. – Arnold, 1930:4 (in checklist of Afrotropical Sphecidae); R. Bohart and Menke, 1976:266 (in checklist of world Sphecidae).

NOMENCLATURAL HISTORY. — The identity of Tachytes pulchrivestitus has never been properly understood since its description more than 110 years ago. Turner treated it as a junior synonym of T. mirus in 1913 and pointed out to its similarity to T. rhodesianus in 1917 (without formally synonymizing these two names). The species was not mentioned by Arnold (1923), but was listed as a synonym of T. mirus by Bohart and Menke (1976). My examination of the holotype in 2019 demonstrates that T. pulchrivestitus is a valid name and a senior synonym of T. rhodesianus Bischoff, 1913 and of T. midas Arnold, 1929 (see below), not a synonym of T. mirus .

SPECIES STATUS. — Cameron did not mention the length of the galea in his original description of T. pulchrivestitus and Turner (1913), when he synonymized this species with T. mirus (apparently without seeing its type), must have thought that both species have an equally elongate galea and the first article of the labial palpus. In reality, the galea of T. pulchrivestitus is longer that wide ( Fig. 9 ), but shorter than the scape (0.7-0.9 × its length), whereas in T. mirus the galea is longer than the scape (about 1.3 × its length). This difference alone precludes the two species from being conspecific. Tachytes pulchrivestitus , therefore, is not a synonym of T. mirus .

RECOGNITION CHARACTERS. — Tachytes pulchrivestitus resembles the species of the basilicus species group in having the setae of the gastral terga golden, arranged in a checkered pattern (as in Fig. 1 ), as well as the palpal formula 6 + 4. Unlike that group, it has the galea longer than wide ( Fig. 9 ) but shorter than the scape (longer than the scape in the basilicus group), the basal article of the labial palp less elongate, and the middle clypeal lobe more prominent ( Figs. 7 and 8 ). In the male, the least interocular distance ( Fig. 10 ) is at least equal to the distance between the ventral ends of the hindocelli (rather than smaller), larger in most specimens. Subsidiary recognition characters are: scapal venter and hindfemoral venter with erect setae; hindfemoral apical lobe narrow, insignificant; female sternum II minutely, closely punctate, with larger, sparse punctures, apical depressions setose; antenna, legs, and gaster all black.

A similar species is T. dilaticornis Turner , which differs by the absence of erect setae on the scape, by the setae of hindfemoral venter inconspicuously short, almost absent, and in the female by a well-defined, round apical hindfemoral lobe. These features were not observed by Arnold (1923). In the male, the basal flagellomeres are conspicuously expanded ventrally, as described by Turner (1916) and Arnold (1923).

JUSTIFICATION OF NEW SYNONYMY. — Arnold (1929:389) differentiated the syntype female of T. midas from the holotype of T. rhodesianus by the details of the scutal punctation and the relative length of flagellomeres I and II. In the first species, according to him, the “anterior third of the mesonotum [correctly: scutum] has a microscopic fundamental puncturation over which is scattered a fairly abundant and larger puncturation” and “the second [correctly: first] joint of the flagellum is very slightly longer than the third [correctly: second] joint”. In the female of T. rhodesianus , the scutum has “a very fine and very close puncturation all over”, and flagellomere I is “a little more than one-third longer than the II joint”. These subtle differences are individual rather than specific: they break down when more specimens are examined.

Also, the lectotype of T. midas and the holotype of T. pulchrivestitus each have six rake spines on foretarsomere I, whereas the holotype of T. rhodesianus and additional two specimens from Zimbabwe have five. This difference is unimportant, however, as the number of the foretarsal rake spines is known to vary individually in Tachytes .

In the original description of T. midas, Arnold (1929:389) claimed that the male genitalia are very different in that species and in T. rhodesianus . I could examine the genitalia of a male syntype of T. midas as well as of four other specimens. In all of them the gonocoxite shows in the lateral view the dorsal spine shortly after its midlength, as in Arnold’s Fig. 12 (for T. midas ), and in most also the preapical spine in the dorsal view, as in his Fig. 13 (for T. rhodesianus ). In the specimen from Zambia, however, the dorsal preapical spine is present only on the right gonocoxite whereas the left gonocoxite is smooth. Evidently, the supposed difference in genitalia does not exist.

In conclusion, T. pulchrivestitus shares all the diagnostic characters with both T. rhodesianus and T. midas and is certainly conspecific with them. As it was described earliest, it becomes the valid name for the species.

GEOGRAPHIC DISTRIBUTION ( Fig. 11 ).— Botswana, South Africa, Tanzania, Zambia, and Zimbabwe. Berland (1942) recorded T. pulchrivestitus from Mali (as T. rhodesianus ), but his identification is not certain.

RECORDS (except the types of Tachytes midas , T. pulchrivestitus , and T. rhodesianus , all other specimens here recorded are from the California Academy of Sciences collections).

BOTSWANA: Serowe (1 ♂) .

SOUTH AFRICA: Limpopo: 21 mi. S Messina (2 ♂) , near Thabazimbi (1 ♂) . KwaZulu-Natal: Mfongosi (1 ♀, determined as T. rhodesianus by G. Arnold), Ntambanana at 28°35ʹS 31°44ʹE (1 ♀, determined as T. rhodesianus by G. Arnold), 10 mi. N Ubombo (1 ♂) . Mpumalanga: Songimvelo Nature Reserve at 26°2ʹ33ʺS 31°00ʹ5ʺE (2 ♂) .

TANZANIA: Tanga Region: Mombo (1 ♀, NRS, holotype of Tachytes pulchrivestitus ) .

ZAMBIA: 32 km E Petauke at 14°17ʹS 31°37ʹE (1 ♂)

ZIMBABWE: Bulawayo (1 ♀, SAM, lectotype of Tachytes midas ) , Bulawayo airport at 20°00ʹS 28°38ʹE (1 ♀) , Bulawayo: Hillside (1 ♂, SAM, paralectotype of Tachytes midas ), Esigodini at 20 ⁰17′S 28 ⁰56′E (Arnold, 1929, as Essexvale), Hwange National Park (4 ♂, as Wankie), Kami (= Khami) Ruins at 20°09ʹS 28°26ʹE (1 ♀, 1 ♂) , Springvale (1 ♀, SAM, holotype of Tachytes rhodesianus ) .

Figures

FIGURES 7–10. Tachytes pulchrivestitus: 7: female clypeus; 8: male clypeus; 9: female galea; 10: male vertex.

FIGURES 1–4. Tachytes mirus: 1: female gaster dorsally; 2: female head in lateral view showing elongate galea; 3: female galea in lateral view; 4: male vertex in dorsal view.

FIGURE 11. Collecting localities of Tachytes pulchrivestitus.