Xylotrechus rameyi Alten, 2014

Alten, Ronald L., 2014, A New Species of Xylotrechus (Coleoptera: Cerambycidae: Clytini) from Utah, Insecta Mundi 2014 (355), pp. 1-6 : 1-4

Xylotrechus rameyi Alten , new species

( Figures 1–4 )

Description. Male ( Fig. 1, 3 ): Robust, cylindrical; integument dark reddish-brown to black; vestiture coarse, appressed, forming pattern of yellow and black integument. Length: 10.5–14.0 mm. Head: With frontal carina broad, flattened, more or less V-shaped with margins irregularly defined above; lower face and genae thinly to densely clothed with yellow pubescence; vertex closely, coarsely punctured and rugulose except for well-defined, margined, obovoid, opaque, minutely rugulose impressions on each side of the median line, separated by about the width of the second antennomere. Area between antennal insertions and eye densely clothed with appressed yellow pubescence; yellow pubescence on vertex/ frons and along lower basal margin of eye moderate to dense, appressed to sub-erect. Antennae: 11 segmented, short, robust, barely surpassing elytral humeri; reddish-brown and darker apically; scape with thin, pale hairs on outer surface, mostly recumbent and becoming sub-erect at apex; antennomeres 2–5 or 6 with reddish-brown hairs, mostly coarse, longest at apex; remaining antennomeres with very short, fine brownish pubescence; length of third antennomere sub-equal to, or slightly longer than scape; 4 th to 6 th antennomeres sub-equal in length and shorter than 3 rd; 7 th through 10 th, sub-equal and shorter than 6 th, 11 th and sub-equal to 6 th. Pronotum: Broader than long and widest near the middle of the basal half; slightly narrowed than elytral humeri; sub-angular; surface of disk coarsely, confluently punctured and carinulate; thinly clothed with pale, sub-erect hairs except basal and apical margins are densely clothed with appressed yellow pubescence; marginal pubescent fascia broadest laterally, narrowing medially; apical fascia typically interrupted at midline by a distance about equal to the width of the antennal scape; basal fascia sometimes interrupted medially lateral limits of the disc irregular in shape but with distinctly delimited margins; surface below lateral margins more finely punctaterugulose, often lighter in color than disk, with shorter, fine pubescence; episternae of mesothorax and metathorax densely yellow pubescent apically; scutellum finely, coarsely punctate, pubescence moderate and present throughout or absent anteriorly. Elytra: Sub-parallel sided; length approximately 2.25 times longer than greatest width at humeri; apices obliquely sub-truncate with outer angle minutely acute; covered with short, dense mostly appressed pubescence; sub-basal spot pale yellow or cream pubescent pattern in an oblique, wedge-shaped form; a median fascia curving forward along suture to base and enclosing scutellum; a somewhat oblique transverse band at apical third, and transverse band at the apex. Legs: Moderately elongated; femora moderately clavate; rufo-testaceous to fusco-rufous; posterior leg with 1 st tarsomere at least twice as long as 2 nd and 3 rd combined. Abdomen: Sternites finely, shallowly, closely punctate; margined with yellow appressed and sub-erect pubescence; decreasing in length from 1 st through 5 th; fifth sternite with apex shallowly emarginated.

Female ( Fig. 2, 4 ): As in the male except form is somewhat larger on average; vertex of head with a narrow, elevated median line and without obovoid depressions; pronotum less angular, and lacking delimited margins at lateral limits of disc; lateral areas of pronotum below disc textured as disc; elytral fasciae bright yellow as on pronotum; median elytral fascia more expanded along base toward humeri and often weakly connected to sub-basal spot by a few yellow hairs; 5 th abdominal sternite longer than 4 th and narrowly rounded or sometimes minutely, narrowly emarginated at apex. Length: 11–17 mm.

Type Material. Male holotype, female allotype ( USNM): UTAH, Kane Co., Mount Carmel Junction, 1.5 miles south of junction state highways 9 and 89A, Elevation , 5,200’ ( East fork of the Virgin River ) ; G.P.S. North 37.20 o ; West 112.69 o. July 31, 2008. R. L. Alten collector, Larvae collected and reared from Box Elder, Acer negundo . R. L. Alten, Collector .

Paratypes: 175: (117) Same data as Holotype ( RAPC): (3) Utah, Kane Co., 3.5 miles SE. Jct. Rt. 9 and Rt. 89A. ( Mt. Carmel Junction ), June 06, 2005. Diapaused adults collected from Gambel’s Oak ; T. S. Ramey, Collector ( TRPC). (10) Utah, Kane Co., 3.5 miles S.E. Jct. Rt. 9 and Rt. 89A ( Mt. Carmel Junction ). June 06, 2005. Diapaused adults collected from Gambel’s Oak. R. L. Alten, Collector, ( RAPC). (2) Utah, Piute Co. , Sevier, June 10, 2006, collected from Gambel’s Oak, J. Cope, Collector ( JCPC). (10) Utah, Kane Co. , 5 miles S. Mt. Carmel Junction , 20 July, 2007, collected from Gambel’s Oak, J. Cope, Collector ( JCPC). (5) Utah, Kane Co. , 7 miles S. Mt. Carmel Jct. , 20 May 2008, Gambels oak, J. Cope, Collector, ( JCPC). (15) Utah, Kane Co. , 5 mi. S. Mt. Carmel Jct. , (ex June 1-29-2010 Acer negundo ), J. Cope Collector, ( JCPC). (9) Utah, Kane Co. , 3 mi. S. Mt. Carmel Jct. , 12 July, 2011. J. Cope, Collector. Collected from Gambel’s Oak, ( JCPC). (4) Utah, Kane Co. , Rt. 89A, 3 miles SE Jct. Rt. 9 Rt. and Rt. 89A, ( Mt. Carmel Junction ), at Coral Pink Sand Dunes Rd. August 01-07, 2011, collected from Gambel’s Oak as larvae and reared by R. L. Alten, ( RAPC) .

Biology. Larval development occurs within the transitional area between living and dead wood. Field observations indicate that infestations can occur in box elder ( Acer negundo , Fig. 9–11 ) and Gambel’s oak trees ( Quercus gambelii , Fig. 12–14). Box elder infestations can be light to severe, so that in some trees, the wood is riddled with hundreds of active galleries, containing a high population density of larvae. This situation has only been observed to occur in box elder trunks, with mature tree trunks on average 12 to 20 inches, and up to 40 inches in diameter, providing a resource sufficient to support large population densities. Because the average Gambel’s oak trunk diameter is only 4 to 6 inches, infestations are comparatively light and scattered within the tree. This explains why the population densities found in oak are relatively low compared to those occurring in box elder. In both host species, the beetles respond in the same manner requiring the same microhabitat for oviposition and larval development.

Dispersal of Xylotrechus rameyi is typical for a species of this genus, with adults usually emerging between May and July. The species may be capable of completing its life cycle in one year, although the life cycle can vary between one to several years before emergence occurs, depending upon annual environmental factors of overall ambient temperature and moisture.

Field observations of X. rameyi indicate that the earliest adult emergence appears to occur on the south-western face of the tree trunks ( Acer negundo , Fig. 9–11 ) caused by the general overall warming effect of solar exposure that produces conditions for accelerated development.

Gravid females appear to be attracted to the cured host wood adjacent to living tissue that is in a distressed condition. In the author’s opinion, based upon a number of field observations, the female is attracted to distressed trees by olfaction, probably being attracted to the collective odor being released from both dead and living wood. Therefore, it is the condition of the trees, rather than the tree species itself that is the predominant factor in determining the stimulus for oviposition and where on the host.

Jim Cope (pers. comm.) observed a female ascending a box elder tree trunk, ovipositing eggs singularly as she moved upward. Larvae have been collected along the entire length of the tree trunk [within this type of microhabitat].

The diapaused adult waits within the pupation cell for warm humid conditions to occur, stimulating emergence. Cold and adverse environmental conditions along with latitude and relatively high elevation often can delay emergence and dispersal well into late spring to mid-summer or even later. During wet and cool years, adult emergence is delayed considerably and during some years completely, as was observed in 2011, when diapaused adults were removed from pupal chambers in Quercus gambelii ( Fig. 12–14) the first week in August. During dry years, the reverse can occur, in that emergence can occur earlier, driven by the lack of moisture and higher diurnal ambient temperatures from clear warm days.

Figures

Figures 1–8. Two species of Xylotrechus. 1–4) Xylotrechus rameyi habitus images, dorsal and lateral views. 1, 3) Male. 2, 4) Female. 5–8) Xylotrechus insignis habitus images, dorsal and lateral views. 5, 7) Male. 6, 8) Female.

Figures 9–11. Box elder (Acer negundo) containing X. rameyi.