Knowltonia Fisher

Westcott, Richard L. & Barr, William F., 2007, Resurrection and review of the genus Knowltonia Fisher, with description of a new subspecies of Chrysobothris Eschscholtz and new species of Acmaeodera Eschscholtz from North America (Coleoptera: Buprestidae), Zootaxa 1481, pp. 49-58 : 49-51

Genus Knowltonia Fisher , resurrected status

Knowltonia Fisher, 1935:117 .

Chrysobothris: Cazier, 1938:17 (synonymy); Fisher, 1942:17 (synonymy).

Type species: Knowltonia biramosa Fisher , by original designation.

Gender: feminine.

Description. Head with clypeus broadly, shallowly, triangularly to arcuately emarginate; eyes separated on vertex by 1.2 to 2.2 times the eye width at middle of head. Antenna with 11 antennomeres, none being laterally compressed; first antennomere elongate and expanded apically; second antennomere short and globular; third antennomere of male elongate, strongly, sometimes acutely expanded on one side or weakly bifurcate at apex, of female elongate, expanded apically with the outer angle distinctly acute to right-angled; antennomeres 4–10 of male densely setose, biramous or slightly to strongly asymmetric, of female short with ventral lobes moderately to widely separated, truncate to slightly rounded apically; antennomere 11 of male forked or asymmetric at apex, of female elongate-oval, usually truncate to subtruncate, or sometimes vaguely acute at apex. Pronotum with front margin truncate to feebly bisinuate and broadly, shallowly arcuate at middle; disk subflattened, laterally convex or swollen, lateral margins ventrad, widely and distinctly indicated, entire or disappearing shortly before front angles, not visible from above. Elytra without or with vague longitudinal carinae, lacking foveae and pubescence; basal margin of each elytron strongly, evenly angulate; lateral margins finely, indistinctly serrate; sutural margins terminating in a tiny acuminate spine or a right-angled tooth; apices broadly rounded, not attaining apex of abdomen, exposing in part 1 or 2 abdominal terga. Legs with profemoral tooth elevated, acute to very narrowly rounded at apex, not serrulate; foretibia of male unmodified. Underside with prosternum flattened at middle, swollen at sides, front margin subtruncate to broadly arcuate, narrowly reflexed or with a reflexed lobe at middle; abdomen with lateral margins entire, ventrites without distinct lateral callosities, fifth ventrite lacking an elevated submarginal ridge.

Discussion: Fisher (1935) described Knowltonia and related it to Chrysobothris . However, he did not discuss any distinguishing character except to say “..differs from all the known genera of Buprestidae in having strongly biramose antennae.” He assumed that the single specimen before him was a male. In his paper describing C. alleni, Cazier (1938) discussed Knowltonia and regarded it as a synonym of Chrysobothris , although we consider his reasoning faulty because it was partly based on incorrect association with such species as C. prasina Horn and C. platti Cazier (the latter presently in Sphaerobothris Semenov-Tian-Shanskij & Richter), and he lacked sufficient material for such a diagnosis. Fisher (1942) formally synonymized Knowltonia under Chrysobothris . His rationale was that he had overlooked Horn’s (1886) male antennal figure for C. atrifasciata LeConte , and that “..more material of Chrysobothris has been available for study and this peculiar character of the males has been found in atrifasciata , biramosa , and alleni ..” To our way of thinking that is no reason for synonymy; it simply enlarges the genus Knowltonia .

We are unaware of further published data under the genus Knowltonia , though Bellamy and Volkovitsh (1997) briefly mentioned it. For some years we and some of our colleagues have considered that it should be recognized at least to subgeneric level. Meanwhile those authors elevated the formerly Old World subgenus C. ( Sphaerobothris ) to genus rank, including in it the North American C. platti and C. ulkei LeConte. Superficially , those species resemble species of Knowltonia but are readily separated by their antennae, which are like those found in most species of Chrysobothris , with no sexual difference and the third antennomere not at all angulate apically. Although the facies of Sphaerobothris seems to distinguish it from Chrysobothris , nevertheless the apparent primary character used by Bellamy and Volkovitsh (1997) to separate them, the width on the vertex between the eyes, is not reliable. In Chrysobothris , this distance was stated to be “equal or less than width of eye”. We examined 25 North American species and found the width to vary from 0.31 – 2.08 times the width of the eye. We found this to range from 1.20 – 2.00 in 12 specimens of S. platti . The character does not appear to be sexual, and it may prove useful in separating some species, at least in Chrysobothris and Knowltonia . We found problems with other characters given in the key to separate Sphaerobothris from Chrysobothris , and subgenera of the former; however, that is beyond the scope of this paper. Nevertheless, we mention it to help justify our position with regards to Knowltonia , which is clearly separable, in a key or otherwise, based on the unique antennal structure of the male. To our knowledge, Fisher’s (1935) statement about that character remains true for New World species; however, two species in the unrelated Australasian genus Castiarina Gory and Laporte have a similar antennal modification.

Members of the genus Knowltonia are moderately elongate and convex beetles, most being various shades of metallic green dorsally ( Fig. 1 ), often with cupreous or, more rarely, bluish overtones; others vary from coppery to dark brown. The elytra usually have violaceous black markings, but may be immaculate. Ventrally, the color varies from light green to dark brown. All species of Knowltonia have been associated with the plant genus Atriplex , from which they have been reared and/or collected. However, there has been considerable misidentification of these beetles.

Males are easily distinguished and separated from those of Chrysobothris and Sphaerobothris by their unique antennae. Other than by facies, which does not always readily separate them from the latter genus, females can almost always be separated from those genera by the shape of antennomere 3. We examined 117 specimens of Knowltonia and found antennomere 3 to be distinctly dilated ventrally ( Fig. 6 ), usually produced triangularly or as a blunt tooth. Though variable, usually the antennae can be considered serrate from antennomere 3; however, on one specimen of K. calida (Knull) this is not so distinct, approaching the odd species of Chrysobothris in form. Antennomere 11 usually is distinctly narrower and more elongate than antennomere 10, not at all laterally compressed and usually more or less truncate at apex where sometimes it is distinctly acute. One specimen each of 57 species of Chrysobothris and two species of Sphaerobothris was examined, representing most if not all the presumed groups of the former found in North America. In all but three species of Chrysobothris the third antennomere is either essentially parallel-sided or slightly swollen apically. Of those three, said antennomere is indistinctly, in two cases more or less acutely, expanded ventrally ( Fig. 9 ), but in no case would we term the antennae serrate from antennomere 3. Antennomere 11 is quadrate, rarely elongate-quadrate, almost always distinctly rounded apically, usually not narrower or more elongate than antennomere 10. The outer antennomeres, including antennomere 11 are laterally compressed in most species of Chrysobothris .

Based on material examined, although most represents K. atrifasciata and K. calida , we suspect that additional taxa exist. However, considering general variability, the similarity of male genitalia, the lack of comprehensive samples of specimens from between known populations of the various phenotypes, and that even the limits between described species seem blurred, we feel this is not the appropriate time for descriptive work. It may be that Knowltonia is like the genus Crossidius LeConte ( Coleoptera : Cerambycidae ), species of which occur in the same habitats and are highly polytypic. Unfortunately, unlike most species of Crossidius , Knowltonia are not commonly collected.

The following key applies almost entirely to populations in the U.S. and should be used with caution for specimens from Mexico. The user is strongly encouraged to use this key in conjunction with the species treatments to follow.

Figures

FIGURES 1 – 3. Dorsal habitus. 1, Knowltonia calida (Knull), female; 2, Chrysobothris socialis socialis Waterhouse, male; 3, Acmaeodera audreyae sp. nov., holotype.

FIGURES 4 – 9. Antennae. 4 – 6, Knowltonia biramosa Fisher: 4 – 5, male; 6, female. 7, K. calida (Knull), male; 8, K. atrifasciata (LeConte), male; 9, Chrysobothris quadrilineata LeConte, female.