Timulla subhyalina Mickel, 1937

Waldren, George C., 2024, Taxonomic notes on velvet ants of the genus Timulla Ashmead, 1899 (Hymenoptera: Mutillidae) in the United States of America and Canada, Insecta Mundi 2024 (55), pp. 1-10 : 11-13

Timulla subhyalina Mickel, 1937

Timulla (Timulla) subhyalina Mickel 1937a: 97 , pl. III, fig. 16. Holotype ♂ (UMSP).

Timulla (Timulla) dubitatiformis Mickel 1937a: 102 . Holotype ♀ (NMNH). New synonym.

Remarks. Mickel (1937a) described the male-based subspecies Timulla subhyalina Mickel, 1937 from specimens from the north-central/northwestern United States and Canada. Additionally, Mickel (1937a) described the female-based species Timulla dubitatiformis Mickel, 1937 from the central and eastern United States. In his remarks for the latter species, T. dubitatiformis, Mickel (1937a) noted: “This female has an exceptionally wide distribution and no male of which the female is unknown has a similar distribution. I am of the opinion that one or all of the group of males including rufosignata , tolerata , subhyalina , hollensis subsp. hollensis , hollensis subsp. melanderi , and sayi represent the male sex. All of these have a more limited distribution than dubitatiformis , and I have attempted without success to find some basis for separating the latter into geographical groups which could be correlated with the above males. The situation may be that the males have differentiated into geographical groups, while the females have remained stable; this has been found to be true of certain other species of Mutillidae both in the United States and the Philippine Islands. All that can be said at present is that the male will probably prove to be among those mentioned above.” The male-based species that Mickel (1937a) referred to above, including Timulla kansana Mickel, 1937 and T. ocellaria , form a species-group which share the following combination of characters: the clypeus is pentagonal and weakly concave, a ventrobasal mandibular tooth may be present or absent, the ocelli may or may not be enlarged, the mesosternal area is weakly armed with an obscure tubercle, and the pygidial process is Y-shaped with the arms of the Y short in length. This species-group is here referred to as the Timulla ocellaria species-group.

Krombein (1953) associated females that keyed to T. dubitatiformis with the male-based species Timulla rufosignata ( Bradley, 1916) from Kill Devil Hills, North Carolina. Krombein (1953) differentiated the newlyrecognized female of T. rufosignata from T. dubitatiformis as follows: “The four females taken in 1952 and the six females captured in 1948 and 1950 are conspecific, key to dubitatiformis in Mickel’s key, and fall within the range of variation he ascribes to that species. They are quite constant in coloration, sculpture, vestiture, and differ from “ dubitatiformis ” females of the metropolitan Washington area in having the last three tergites with ferruginous integument, the scutellar scale evanescent or absent, and the posterior surface of the propodeum more coarsely sculptured, with a few longitudinal ridges and a tendency toward the development of small asperites on the upper third. The Kill Devil Hills series differs from the type of dubitatiformis from Boulder, Colorado in the same particulars.”

Mickel (1937a) attempted to find some distinction between specimens across the broad geographic distribution of T. dubitatiformis that could correspond with the more limited distributions of males of the T. ocellaria species-group. I attempted to do the same and in the end, I was unsuccessful like Mickel despite examining 286 T. dubitatiformis specimens. The characters that Krombein (1953) ascribes to the females he associated with T.rufosignata fall within the variation of T. dubitatiformis throughout its distribution. There is no apparent geographic pattern with the characters that Krombein (1953) emphasized. Krombein’s association, however, does confirm the relationship between T. dubitatiformis and members of the male-based T. ocellaria species-group. The type locality of T. dubitatiformis is Boulder, Colorado, and the only male-based species of the T. ocellaria species-group that occurs in Colorado is T. subhyalina . Further, the only other species of Timulla that occur in Colorado are T. barbigera , T. grotei , T. oajaca , T. suspensa and T. vagans , all of which are known from both sexes ( Mickel 1937a; pers. obs.). To the northwest, the only species of Timulla that occur in Washington state are T. dubitatiformis and T. subhyalina . Based on shared membership in the T. ocellaria species-group and overlap in distribution, Timulla dubitatiformis Mickel, 1937 is here considered a new synonym of Timulla subhyalina Mickel, 1937 .

This taxonomic action generates a challenge in that although I consider the holotype of T. dubitatiformis to be a synonym of T. subhyalina , not all T. dubitatiformis females sensu Mickel (1937a) can now be considered conspecific with T. subhyalina as they belong to other male-based species of the T. ocellaria species-group. I have labeled all T. dubitatiformis females (sensu Mickel (1937a)) that I have examined in collections as ‘ Timulla dubitatiformis ’ despite awareness of this name eventually being synonymized. Due to their apparent morphological uniformity, assigning the name ‘ Timulla ocellaria species-group’ for females of the former species T. dubitatiformis is the suggested approach moving forward post-synonymy. All members of the T. ocellaria species-group are now effectively known for both sexes with the recognition that the former female-based species T. dubitatiformis is in reality a morphologically-conservative complex of species (with the males being Timulla hollensis ( Melander, 1903) , T. kansana Mickel, 1937 , T. ocellaria Mickel, 1937 , T. rufosignata ( Bradley, 1916) , T. sayi ( Blake, 1871) , T. subhyalina Mickel, 1937 , and T. tolerata Mickel, 1937 ).

Material examined ( Timulla dubitatiformis ) ( 2 ♀). Holotype: USA: Colorado: Boulder Co.: Boulder, 26.May.1908, T.D.A. Cockerell (1♀ – NMNH – USNMENT 01546530 ). Non-type (s): USA: Washington: Whitman Co. : Pullman, 08.Jul.1976, P.J. Landolt (1♀ – FSCA).

Material examined ( Timulla subhyalina ) (5 ♂). Non-type(s): USA: Colorado: Sedgwick Co.: Julesburg, 20–27. Aug.2001, Irwin & Parker, “MT” (4♂ – EMUS). Washington: Whitman Co.: Colton, 10 mi. S, 16.Sep.1982, W.J. Hanson (1♂ – EMUS).

In total, 286♀ of Timulla ocellaria species-group females (i.e., Timulla dubitatiformis (sensu Mickel 1937a)) were examined ( AMNH, ASUHIC, AUEM, BPBPM, CASC, CMNH, CNC, CSUC, CUIC, DEBU, DGMC, EMEC, EMUS, FHSM, FMNH, FSCA, GCWC, INHS, KSUC, LSAM, MCZ, MEM, MSUC, MTEC, NCSM, NMNH, OMNH, OSAC, OSEC, PMAE, PMNH, PERC, SDMC, SDSU, SEMC, TAMU, UAAM, UCMC, UGCA, UKIC, UMMZ, UMRM, UNSM, UTIC, WFBM, WIRC, WSU).

In total, 143♂ of Timulla subhyalina Mickel, 1937 were examined ( AMNH, CMNH, CNC, CSCA, CSUC, CUIC, DGMC, EMUS, FHSM, FMNH, FSCA, GCWC, INHS, MCZ, MEM, MSUC, MTEC, NMNH, OSAC, OSEC, PMAE, PMNH, PERC, SDSU, UAIC, UCDC, UCMC, UCRC, UGCA, UMRM, UNSM, WFBM, WIRC, WSU).