Dryotribodes, Zimmerman, 1942

Zimmerman, Elwood C., 1942, Curculionidae of Guam, Insects of Guam I, Honolulu, Hawaii: Bernice P. Bishop Museum, pp. 73-146 : 132-134

Genus DRYOTRIBODES , new genus

Body comparatively slender, derm coarsely sculptured, finely and sparsely setose. Head subconical, not quite as long as broad, with crown separated from front by a distinct dorsal impression which may or may not continue laterally as a conspicuous postocular constriction; eyes coarsely faceted, slightly to moderately protuberant, somewhat more widely separated below than above, separated from prothorax by more than length of an eye, interocular area narrower than base of rostrum. Rostrum, beyond eyes, distinctly longer than head, about two thirds as long as prothorax, at least twice as long as basal breadth of rostrum, subcylindrical and but slightly arcuate behind antennae, expanded, somewhat compressed and more strongly arcuate beyond antennae; antennae inserted at or slightly beyond middle and distinctly more than length of an eye in front of eyes; scrobes passing rapidly downward well below eyes. Antennae with scape reaching to or distinctly beyond hind margin of eyes, but directed well below lower margins of eyes when at rest, longer than funicle excluding club; funicle 7-segmented, first or first and second segments longer than any of the other segments which become successively more transverse; club elliptical, shorter than preceding part of funicle, its basal segment densely setose. Prothora:i: slightly longer ilian broad, subtubular, constricted before apex, subtruncate at base. Sc1,tellmn not visible. Elytra only slightly broader at base than base of prothorax, evidently nine- or ten-striate, some striae incomplete and irregular, usually some intervals cariniform. Wings evidently non-functional. Legs with femora moderately clavate, edentate, hind pair reaching almost to apex of second ventrite; tibiae not much longer than tarsi, comparatively slender, unci and mucrones well developed; tarsi with second segment about as long as broad, third broader than secoi;id,entire, emarginate, or bilobed, 4 extending beyond 3 for a distance distinctly greater than length of 3. Sternmn with fore coxae nearer hind margin than to fore margin of prosternum, intercoxal process distinctly narrower than breadth of a coxa; intercoxal process of mesosternum narrower or as broad as breadth of a mesocoxa; metasternum about as long between mid and hind coxae as length of first ventrite, metepisterna mostly concealed, at most narrowly exposed behind, metacoxae separated by more than longitudinal diameter of a coxa and narrowly separated from elytra, intercoxal process subtruncate. Venter with first two ventrites fused, 3 and 4 subequal, together shorter than either 2 or 5.

Genotype: Dryotribodes obscurus , new species.

This genus is closely allied to Dryotribus Horn, 1873 , but it may be easily separated from that genus because of its 7-segmented funicle. The only major difference between Dryotribodes and Dryotribus is this antenna! character. However, this difference is sufficient to place the two genera in two different subtribes, according to existing schemes of classification. The two genera obviously have a common ancestral relationship and their separation into different subtribes would be incorrect. The division of the Cossonini into major groups based on the number of segments in the funicle is a convenient one, but it is unnatural, because such closely allied genera as these are placed far from each other and their true relationships are obscure.

Sir Guy Marshall has kindly examined the genotype of this new genus and compared it with the British Museum material. He writes, "Among the 7-jointed genera it comes closest to Pholidophorus Woll. from Japan, but this is a winged genus with projecting shoulders "

All of the species of Dryotribodes greatly resemble Dryotribus and one would place them in Dryotribits without hesitation if the antennae were not examined.

On the genotype, the third tarsal segments are deeply and unquestionably bilobed, but on D. angularis they are emarginate and on D. denticulatus they are almost entire and only slightly emarginate. This difference in the third tarsal segment is often of major importance, but here it breaks down to a specific character. On both D. obscurus and D. angularis the postocular constriction is conspicuously marked on the sides of the head, but on D. denticulatus the constriction is not indented on the sides and makes only the dorsum emarginate. On D. angularis the constriction is deeply and very sharply marked dorsally, laterally, and ventrally; D. obsrnrus is intermediate between this and D. dentirnlatus. On D. angitlaris the intercoxal process of the mesosternum is distinctly narrower than the breadth of a mesocoxa; on D. denticulatus it is about as broad as a coxa and on D. obscurus it is slightly broader (10:9). On D. obscurus and D. angularis the antenna! scape is enlarged gradually from the base to the apex and has no distinct club. On D. denticulatus , however, the scape has a slender stalk and a distinct club. On D. angularis the scape reaches the hind margin of the eye, on D. obscurus it extends behind the eye to the cephalic constriction, and on D. clenticulatus it reaches past the cephalic constriction almost to the prothorax.

The discovery of representatives of this new genus at such widely separated localities as Guam and the Marquesas, over 5,000 miles to the southeast at the opposite sides of Oceania, is an example of extreme discontinuity of distribution. This discontinuity is surely not actual, however, because our knowledge of the absolute distribution of the Curculionidae is so incomplete at this early stage in the entomological exploration of the Pacific as to be misleading. Other species will probably be described from the intervening islands. Unfortunately, I do not now have access to the extensive collections of Cossoninae made by me in southeastern Polynesia in 1934. There may be other species in that collection.

KEY TO THE SPECIES OF DRYO'l'RIBODES

1. None of the discal elytral intervals conspicuously elevated more than the others, the fourth entire and as prominent as the others; third tarsal segment deeply bilobed; Guam............................................................37. D. obscurus Zimmerman.

At least the third and fifth elytral intervals elevated and more prominent than the others, fourth at least partially obscured, or incomplete and distinctly less prominent than the others; third tarsal segment not bilobed; Guam.......................2

2. Antenna! scape reaching only to the hind margin of eye, not extending beyond the cephalic constriction; cephalic constriction deeply and sharply marked entirely around the head; prothorax with a distinct subbasal constriction; second and third elytral intervals equally elevated on the declivity; Guam.......... TODO TODO TODO TODO

Antenna! scape reaching past the cephalic constriction; cephalic constriction poorly developed and not at all sharply and deeply impressed, prothorax without a subbasal constriction; second interval not elevated; the sides of the elytra appearing conspicuously denticulate from above; Marquesas TODO TODO TODO