Chrysobothris dudleyaphaga Westcott

Westcott, Richard L., 2007, A new species of Chrysobothris Eschscholtz feeding on Dudleya spp. (Crassulaceae) from California and Baja California, with biological, distributional and taxonomic notes on other North American Buprestidae (Coleoptera), Zootaxa 1630, pp. 23-37 : 24-32

Chrysobothris dudleyaphaga Westcott , new species

( Figs.1–6 , 8–9 )

Holotype male: 9.9 mm long, 4.3 mm wide, above broadly convex, moderately shining, black with coppery reflections, beneath shining bluish black with strong purplish cupreous reflections; head with front reddish coppery with areas of green or golden-green, front margin of clypeus green; pronotum with purplish coppery reflections in punctured areas; elytra with bright coppery reflection in foveae, with coppery to reddish coppery reflections on sides and, more pronounced, apically.

Head more or less flattened, with a pair of smooth, irregularly rounded callosities at middle of front and a well-developed elevated chevron above, with a fine median longitudinal carina that extends through chevron to middle of frons; surface coarsely, rather evenly reticulate-punctate and moderately clothed with long, mostly erect white setae; clypeal margin broadly deeply triangularly emarginate along middle, strongly oblique laterally; antennae golden green becoming largely black apically, conspicuously serrate from fourth antennomere which is 3/4 as long as third, third antennomere elongate-subtriangular and twice as long as second, antennomeres 4–11 gradually narrowed.

Pronotum twice as wide as long, widest at posterior third, slightly wider at base than apex; sides slightly converging anteriorly from basal third, strongly oblique posteriorly; lateral margins indistinct near apex, slightly arcuate to basal third, then strongly convergent to subrectangular hind angles; anterior margin shallowly emarginate, with a feebly-developed broad median lobe; posterior margin evenly arcuate in front of elytra, with a shallowly arcuate median lobe; disc broadly convex, slightly flattened at sides, with a distinct median depression between two large, smooth irregular anteromedian callosities that are more or less connected laterally with another, smaller, irregular callosity, and with distinct broad oblique lateral depressions extending from basal third to near apical angle, there joining similar transverse depressions that extend 3/4 of the way to middle; surface coarsely densely rugose-punctate, punctures smaller and denser in median depression, confused apically and laterally, moderately clothed with long erect white setae except sparsely so on apical half.

Elytra distinctly wider than pronotum, 1 3/4 times long as wide; bases broadly evenly rounded; sides subparallel from humeri to apical third, then gradually converging to rather broadly rounded apices; lateral margins very weakly serrate throughout; basal depressions rounded, very deep; humeral depressions elongate, rather shallow; each elytron with four distinct longitudinal costae, first three much more pronounced, the first elevated apically and extending from near base to apex, second extending from base and ending well before apex, third arcuate anteriorly and extending from back of umbone, where it joins the fourth, to about apical third of elytron, fourth much narrower and irregular, especially basally, extending from umbone to just beyond second, and each elytron with three shallow densely punctured foveae, the first much larger and almost interrupting second costa at about basal 1/3, the second at apical 2/5, interrupting third costa near apex, the third indistinct at apical 1/3 between first and second costae; surface mostly rather densely punctured, finely punctured apically, becoming coarsely, more densely and rugosely so basally, punctures confluent laterally on apical half and mostly smaller than on pronotum; moderately clothed with long erect to suberect white setae.

Prosternum strongly depressed behind anterior margin that is moderately deflexed and with a very broad, weakly-developed median lobe; surface with a moderately broad smooth black median line, coarsely densely punctate on middle, becoming more sparsely rugosely punctate laterally, densely clothed with long erect white setae.

Abdomen with pygidium rather finely moderately evenly punctate, apex shallowly arcuately emarginate; beneath finely, rather sparsely punctate at middle becoming more densely punctured at sides of ventrites 1 and 2 and on ventrite 5, median punctures of ventrites 2-4 with broad elongate, very shallow grooves behind which they are much reduced, scarcely evident on ventrite 5, surface moderately clothed with long subrecumbent white setae; all ventrites with well-developed smooth lateral callosities; last visible ventrite with lateral margins rather strongly and evenly serrate, without a submarginal ridge but slightly thickened on either side of broad deep arcuate apical emargination.

Legs with femora and tibiae coppery, tarsi bluish-black with faint coppery reflections; profemur with a large well-developed broad equilaterally triangular tooth that is coarsely denticulate on outer margin; protibia scarcely arcuate, with a well-developed broadly rounded dilation just behind apex; mesotibia straight, slightly expanded apically; metatibia straight.

Genitalia as in Fig. 3 .

Allotype female: 10.8 mm long, 4.9 mm wide, differs from holotype as follows: head colored a mixture of reddish-coppery and brassy, front margin of clypeus shining bluish black; antennae with but faint greenish reflections, first (especially) three antennomeres coppery; prosternum slightly less densely clothed with setae, heavily and coarsely punctate on middle and without median line; abdomen with pygidum coarsely densely punctate, apex truncate; last ventrite with narrower and shallower apical emargination; pro- and mesotibiae unmodified.

Material examined: Holotype male ( CASC No. 18332) labeled “ MEX, BajaCalif.N., 9.3 mi SW Colonet, 24-VI-1987, R. L. Westcott/Flats along coast, living rosette DUDLEYA INGENS / HOLOTYPE Chrysobothris dudleyaphaga , R. L. WESTCOTT”; allotype ( CASC) from CALIFORNIA, San Diego Co., Otay Mesa, Jct. Otay Valley & Heritage Roads, em. 9-VI-78, reared from Dudleya edulis, B. K. Dozier. Paratypes as follows: 23 M, 17 F, same data as holotype; 22 M, 20 F, same except 7-VII-88, C. L. Bellamy, Westcott & Mühle; also from MEXICO, Baja Calif. N., 1 F, Rosarito Beach, dug from Dudleya sp. intercepted at San Ysidro, California, 27-VI-62, E. D. Algert; 11 M, 6 F, 8.7 mi SW Colonet, 9-VI-85, D. Faulkner; 2 M, 4 F, 6.6 mi SW Colonet, 18-VI-87, living rosette D. ingens ; 6 M, 1F, 16 mi N El Rosario, 19 & 23-VI-87, D. cultrata ; 2 M, 7 mi N El Rosario, 23-VI-87, D. cultrata ; 3 F, 1 mi E Rodríguez Dam, Hwy. 2, Km 164, slopes above railroad, reared from D. edulis plants collected 9-V-77, em. 29/V-28-VI-77, and 1 M, same data except cut from pupal cell, 3-XII-79, all R. L. Westcott. CALIFORNIA, same data as allotype except as indicated: 3 M, cut from pupal cell, 15-IV & 4-VI-78; 3 M, 4 F, em. 21/V-28/VI-78; 2 M, host coll. IV-1977, em. 17-24-VI- 78; host coll. 21-IV-79, 1 F, em. 27-IV-79; 2 F, cut out 9-VI-79; 1 F, host coll. V-81, cut from pupal cell 15-VI- 82; 1 M, 4 F, reared from pupal cells coll. V-1984, em. 1985 & 1986, all B. K. Dozier; host coll. 9-V-77, 5 M, em. 29-V-10-VI-77; 1 M, em. spring, 1979; 1 M, em. 12-VII-80; 1 M, host coll. 27-VII-77, em. 12-V-78; 1 M, dead in pupal cell 27-VII-77, all R. L. Westcott; San Diego Co., Otay Mesa, 1 M, cut from pupal cell in Dudleya , 26-V-84; reared from Dudleya sp., pupal cells coll. 26-V-84, 1 F, em. 3-VI-84; 1 F, em. 15-VI-84; 3 M, 1F, em. 10-VII-84, all B. K. Dozier; 1 F, Old Mission Dam, 9-VI-78, Faulkner & Brown; Orange Co., 1 F, Laguna Beach, 9-V-47, on Eriogonum fasciculatum, D. S. Verity. Paratypes deposited in CASC, CICESE, CIDA, CLBC, CSCA, DSVC, FSCA, HMMC, LACM, RLWE, SDMC, SGWC, TCMC, UCDC, USNM, WFBM.

Distribution: California and Baja California Norte ( Clark & Westcott,1992); known for a distance of about 440 km from Laguna Beach to near El Rosario.

Variation: As in perhaps most others of its species-group, C. dudleyaphaga is highly variable. Size: overall, the specimens examined range from 6.8–11.7 mm. In a sample from the northern population in D. edulis , 18 M ranged from 9.2–11.4 mm (average 10.2 mm) and 14 F ranged from 10.1–11.7 mm (average 10.9 mm). In a sample from the type locality near Colonet on D. ingens , 15 M ranged from 7.1–9.8 mm (average 8.9 mm) and 15 F ranged from 7.7–10.4 mm (average 9.4 mm). The apparently smaller average size of beetles from the latter site is not related to host, as D. ingens is a considerably larger plant. A likely reason is that rainfall is lower in the south.

Head: color of the front in the male ranges from dark or bright reddish or purplish copper to almost entirely bright green or golden green with light to strong coppery reflections, while the clypeus almost always is green or greenish, and the chevron and vertex vary from coppery to purplish; front in female variably black with purplish-coppery reflections to entirely coppery red or green much like in the male; punctures moderately to densely placed, those on the middle may not be reticulate. The median frontal callosities occasionally are ill defined, and rarely there is an additional, very irregular and usually poorly defined pair above and slightly mesad of antennal sockets. The frontal chevron very rarely is strongly flattened and interrupted by punctures, and the longitudinal carina on the vertex may or may not extend below the frontal chevron and may be finely grooved. Pronotum: considerable variation exists in the development of rugosities, raised smooth areas and anteromedian callosities, though the latter are always clearly evident, especially the mesal pair; the median longitudinal depression varies from absent to extensive and moderately depressed, a median carina may be present and well developed therein, and the punctation is quite variable depending upon to what extent the depression is developed. Lateral margins are strongly (usually) to very weakly oblique posteriorly. Elytra: costae are quite uniform and all four always distinct; first two may be variably disrupted basally by rugae and punctures, and the second may be completely interrupted by basal fovea; the last three costae vary in extent and apical joining. On each elytron the apical foveae may merge, usually by a very fine connection that partially interrupts the second costa; the mesal of these two foveae may be greatly reduced or absent. The foveae tend to be more distinct in the northern populations, which are in Dudleya edulis . The lateral margins range from indistinctly to distinctly—though not strongly—serrate apically. Prosternum: the median lobe of the front margin varies from weakly to very strongly developed; the median line is extremely variable, often scarcely definable, or it may be absent—it may be represented by a very broad, coarsely punctate black area, especially in females. Abdomen: color ranges from dark purplish coppery to shining copper. The last ventrite exhibits lateral margins varying from strongly and evenly to very weakly and unevenly serrate, and the apical emargination of the female varies in width and depth but is uniform in shape. Legs: the profemoral tooth occasionally is only moderately developed, though its acuteness varies considerably.

Comparison and taxonomy: In Fisher’s (1942) key C. dudleyaphaga should run to C. oregona Chamberlin or C. pubescens Fall. Based on general appearance, the long white vestiture of the dorsal surface, and the shape of the aedeagus, it appears most closely related to the latter. It may be distinguished from both species by its more robust appearance, usually larger size, and by each elytron bearing four very well developed and strongly elevated costae—there are four more or less distinct costate in C. oregona but they are never so strongly developed, especially towards the base. Chrysobothris dudleyaphaga also appears closely related to the common and highly variable C. mali Horn (Pacific flatheaded borer), which often is a destructive pest and undoubtedly has more hosts than any other buprestid in North America. Although the latter is a smaller species, specimens of the two can be comparable in size. The much longer and denser dorsal vestiture, the more prominent elytral costae and, usually, the indistinctly serrate apical portions of the elytra of C. dudleyaphaga readily separate them. Some difficulty may be encountered if specimens of C. dudleyaphaga have the median pronotal depression lacking or feebly indicated, in which case they may key to C. subcylindrica Motschulsky ; however, that species averages smaller in size, is less robust, has shorter elytral vestiture and the aedeagus markedly different; and its only known hosts are in Asteraceae .

Chrysobothris dudleyaphaga belongs to a taxonomically difficult group of species that are generally characterized by the presence of distinct, usually moderately to densely placed setae, notably on the elytra. With a few possible exceptions, this “hairy group” can be divided into two subgroups: 1) more depressed species such as C. mali and C. idahoensis Barr , and 2) more convex species such as C. subcylindrica and C. deserta Horn ; C. dudleyaphaga belongs to the first subgroup. Most species of the “hairy group” appear to be in a high state of evolutionary plasticity, which sometimes mirrors that of the plant genera or species they utilize as hosts. Notable examples include a variety of species that feed on the genus Eriogonum (wild buckwheat). On the other hand, it is tempting to explain at least part of the extreme variation exhibited by C. mali to its use of a wide variety of hosts. Much more study of this group is necessary to define its species limits, however this is hampered in that many of them are poorly represented in collections— C. mali is a notable exception—and their small size, usually dull coloration, and cryptic habits make them easily overlooked by collectors.

Biology: Chrysobothris dudleyaphaga is primarily a denizen of the Californian coastalscrub biotic community ( Pase and Brown, 1982), though its southernmost known distribution extends slightly into the Vizcaíno subdivision of the Sonoran desertscrub ( Turner and Brown, 1982) along the coast in what I would call a transition zone. Adults of C. dudleyaphaga were taken in the latter region on C. cultrata , and larvae presumed to be that species were found in D. attenuata in the same general area on 12-VII-88, 35 km. S of San Quintín. At the type locality ( Fig. 7 ) prominent plants besides the host D. ingens include Agave shawi , Ambrosia sp., Atriplex sp., Cylindropuntia sp., Euphorbia misera , Ferocactus sp., Frankenia palmeri , Mammillaria dioica , Mesembryanthemum crystallinum and Simmondsia chinensis . At the site (Otay Mesa and Heritage roads; Fig. 10 ) from where most specimens were reared from D. edulis ( Fig. 11 ), associated plants were Eriogonum fasciculatum , Ferocactus viridescens , M. dioica , Cylindropuntia sp. and S. chinensis . The beetle exhibits for the family an interesting adaptation by using as hosts species of the succulent genus Dudleya , and that it occurs in areas of relatively low temperature and sunshine. Over the range of C. dudleyaphaga , climate includes average annual temperatures ranging from about 15.5–18 C and rainfall from about 80– 265 mm; for example, at Presa Rodríguez the figures are 17.6 C (19.7 C in June) and 214.5 mm (0.4 mm in June) ( Hastings & Humphrey, 1969). Adults feed on the succulent leaves of their hosts ( Figs. 8–9 ), even during periods of overcast skies and relatively cool temperatures, and are uncharacteristically inactive in contrast to the behavior of most Buprestidae , which normally are heliophilic and thermophilic. An adult was observed feeding on its host at 8 a.m. (PDT), with the temperature only 18° C. Chrysobothris dudleyaphaga appears to exhibit behavior more befitting a weevil than a buprestid.

Larvae ( Fig. 4 ) have been found in two general types of plants, those with the caudices—in which they feed—relatively thin (± 0.5–3 cm) and usually branched ( D. attenuata and D. edulis ), and those with the caudices much thicker (4 cm or more) and often unbranched (e.g. D. ingens ). These are highly succulent plants, but the caudex of the larger species may be quite woody, especially externally. In D. ingens , several larvae have been found in a single caudex (B. K. Dozier, pers. com.). In D. attenuata (see above), larvae have been found inside caudices with diameters not much larger than themselves. In that species and D. edulis , only one larva per caudex has been found, its extensive feeding causing the death of that portion of the plant in D. attenuata and usually so in the much thicker D. edulis . Attack by C. dudleyaphaga does not seem to pose a threat to the entire plant, perhaps partly because it is not a particularly abundant species. However, the associated Rhagea stigmella (Dyar) ( Lepidoptera : Pyralidae ) was observed in D. edulis near Presa Rodríguez causing extensive damage, including death of the entire plant. The coarser frass of the moth larva distinguishes its damage, though it may be difficult to ascertain in examples of very old dead plant material. Westcott (2005) discussed a similar association between Chrysobothris eriogoni Westcott and the clearwinged moth, Synanthedon polygoni (H. Edwards) ( Lepidoptera : Sesiidae ). Another associate, Tricorynus dudleyae White ( Coleoptera : Anobiidae ), was reared from D. edulis infested with C. dudleyaphaga , and it works in dead caudices ( White, 1981). One specimen of the predator Cymatodera ovipennis LeConte ( Coleoptera : Cleridae ) was reared from a stem of D. edulis wherein it had been feeding on a larva of C. dudleyaphaga , and larvae presumed to be that clerid were found in the field associated with the buprestid larvae. At the type locality, a subadult Xysticus sp. near montanensis Keyserling ( Araneae : Thomisidae ) was found with an adult beetle as its prey.

Larvae of C. dudleyaphaga appear to feed within living tissue during much of their development, something I have also observed in related species that feed in roots, caudices and stems of small shrubs and perennial herbs that occur mostly in arid or semi-arid regions of the western U.S. My rearing attempts substantiate that larvae of these related “hairy group” species are intolerant to water loss, much more so in their earlier instars. Unless host material is gathered when it contains at least mature larvae, most attempts to rear adults proved unsuccessful. This contrasts with most species in the genus, which feed in dead or moribund wood of branches and trunks, many of which live in very dry environments. Subsequent rearing attempts by F.M. Beer (pers. comm.) and me substantiate observations made by Beer (1949) that in such species emergence of adults is not substantially affected by drying, although from evidence to date it appears that most are incapable of extended larval development unlike some species in genera such as Acmaeodera and Buprestis that may spend many years in dry wood yet still emerge as adults ( Beer, 1949; Smith, 1962).

The larva of C. dudleyaphaga seems to have at least partially overcome the drying problem by forming a relatively impervious pupal cell, at least in D. edulis . These extremely hard pupal cells are remarkable. I found them by breaking open infested caudices of C. edulis— I did not find cells in other hosts, but spent little time investigating there. Irregularly round or oblong, these cells ( Fig. 5 ) are made from very tightly packed and cemented frass. They are very rough externally, smooth internally, and can be easily disregarded if one is not careful to break away all the looser frass surrounding them within the caudex. I have not observed such a discrete pupal cell during my extensive examination of the aforementioned “hairy group” of species that occupy a similar niche in host plants of the genus Eriogonum (e.g. see Westcott, 2005), nor in my limited experience with other species of Chrysobothris . I suggest that the hard pupal cell of C. dudleyaphaga represents foremost an adaptation to conserve moisture, especially considering the xeric habitat in which this species occurs, and surely it deters predators. In the laboratory, I found live larvae (or prepupae) still in the cells more than two years after they were collected, though the cells were subjected to an occasional sprinkling. When removed from their cells they desiccated quite rapidly. A perfectly formed, though abnormally small, adult emerged after three years. It seems that the pupal cell also could serve to mitigate the effects of excessive moisture on the organism within, since its location in dead or dying plant material would render the developing insect more susceptible to water penetration than if the cell were formed within living tissue. The effectiveness was not ascertained. However, in some instances it failed to prevent the apparent effects of an abnormally wet winter and spring of 1978–1979 when, during IV-1979, numerous larvae, pupae and adults were found consumed by fungus within their pupal cells (B.K. Dozier, pers. com.).

Clues to the phenology of C. dudleyaphaga are limited, based on few observations. Collections in the Colonet area of Baja California indicate that adults are most likely encountered from early June to early July. Farther north, at the site in San Diego Co., California, only one adult was seen in the field, that being on 9-V- 77 when host plants where gathered. Rearing records from there seem to indicate most emergence occurs between mid-May and mid-June. B.K. Dozier (pers. comm.) found two slightly teneral adult males in their pupal cells on 15-IV-78, at the same time observing three pupae that were just beginning to darken. However, at the same place I extracted pupal cells on 27-VII-77 and found them to contain prepupae. At that time I found three disparately sized small larvae feeding in living stems. No such larvae were found that May. While a concerted effort to study the biology of this species is necessary before a definitive conclusion can be drawn, it is my opinion that a one-year life cycle is possible given a good year. However, from the data provided herein it seems obvious that two years or more may be required, especially during dry years. Pinto (1977) discussed adaptation to drought in desert blister beetles ( Meloidae ).

Discussion: As noted in the introduction, according to B. K. Dozier (pers. comm.), surely the first knowledge of C. dudleyaphaga is based on larvae intercepted several times from Baja California, Mexico, at San Ysidro, California, cut from Dudleya spp., notably plants that were taken from the Rosarito Beach and Cabo Colonet areas, the latter being very close to the type locality. As noted among the paratypes, only one adult was found among those interceptions. In 1977 I observed buprestid emergence holes ( Fig. 6 ) in D. ingens on Colonet Mesa and D. cultrata at 7 mi N El Rosario, both of which later proved to be from C. dudleyaphaga , and in Dudleya sp. far to the south in San Andreas Canyon, near Punta Prieta. Since at that time no species of Buprestidae were recorded from Dudleya or any other genus in Crassulaceae , I assumed that all observations referred to C. dudleyaphaga . However, later, the inherent danger of assumption became apparent when I broke open a pupal cell at San Andreas Canyon and found an adult of the entirely unrelated C. schaefferi Obenberger (see below)! That species has been collected almost exclusively in desertscrub and thornscrub (Brown, 1982); however, I have seen a specimen from 17 mi S of Santo Tomas, which is in the Californian coastalscrub community but of a different vegetational makeup than where C. dudleyaphaga has been collected. Previously, the only known host for Chrysobothris schaefferi was based on a specimen reared from Bursera microphylla in California ( Nelson, 1966), though in Baja California other collectors and I have taken adults on a wide variety of plants, largely trees and woody shrubs in the family Fabaceae . In contrast, C. dudleyaphaga long escaped attention, perhaps because it occupies a rather cryptic niche, using only Dudleya spp. as hosts, and occurs in the Californian coastalscrub, an area that has not been well collected by students of Buprestidae . I think that buprestid feeding damage in Dudleya spp. from said region is almost certainly due to C. dudleyaphaga , but as one proceeds south into the Vizcaíno subdivision, identity must be confirmed from associated adults until such time as it can be ascertained from the larva or damage.

When I visited the collecting site for C. dudleyaphaga at Otay Mesa and Heritage roads in July, 1988, ongoing development was seen nearby, and this threat caused me to choose a different type locality. Now, based on a recent aerial photograph available at Google Maps (http://maps.google.com/maps?tab=wl), only one corner of that particular, now major, intersection remains; it and nearby areas are crisscrossed with ORV trails and clearings. The type locality and surrounding habitats are not free from threat either. For information concerning this, I refer the reader to Wikipedia: http://en.wikipedia.org/wiki/ Punta_Colonet,_Baja_California. Also, I have seen large areas of this habitat type cleared, ostensibly for agriculture, but much of it simply remains fallow. Nevertheless, I feel that the future of C. dudleyaphaga in Baja California remains reasonably secure because there is extensive habitat, some of it quite remote, and there is lack of water to develop it all. However, unfortunately we cannot say the same thing with regards to southern California!

Figures

FIGURE 7. Type locality, general aspect of habitat, July 1988.

FIGURES 1 – 6. Chrysobothris dudleyaphaga, sp. nov.: Figs. 1 – 2, adult dorsal habitus, 1, female and 2, male, from San Diego Co., California; Fig. 3, aedeagus from type locality; Fig. 4, larva from Dudleya edulis, San Diego Co.; Fig. 5, pupal cells from Dudleya edulis; Fig. 6, adult exit hole in Dudleya ingens.

FIGURES 8 – 9. Adults at type locality, July 1988: Fig. 8, adult on host, Dudleya ingens; Fig. 9, adult feeding on same host.

FIGURES 10 – 11. Otay Mesa & Heritage Roads, San Diego Co., California, July 1988: Fig. 10, general aspect of habitat; Fig. 11, host, Dudleya edulis.