A New Species of Ceratognathus Westwood (Coleoptera: Lucanidae) from New Zealand

Transactions of the Royal Society of New Zealand : Zoology, Volume 2, Issue 12, 29 July 1962, Page 69

A New Species of Ceratognathus Westwood (Coleoptera: Lucanidae) from New Zealand

Beverley A. Holloway

By

[Received by Editor, February 9, 1962.]

Abstract

Ceratognathus passaliformis n.sp. is described from a series of specimens collected in the Orongorongo Valley, near Wellington, New Zealand. The specimens were found in nests of an endemic formicine ant, Prolasius advena (Fr. Smith), under beech logs.

Stag beetles belonging to the genus Ceratognathus Westwood occur in Tasmania, eastern Australia, and New Zealand. The new species described in this paper was found in ants’ nests in the Orongorongo Valley, near Wellington, New Zealand, and is one of the smallest species of the genus. Eleven other species of Ceratognathus are known from the New Zealand area (Holloway, 1961). The new species was discovered by D. Edwards and J. Balderson, who very kindly presented the writer with all the material they collected. Mr Edwards later accompanied the writer and other members of the Dominion Museum staff to the original collecting area, where further specimens were found.

Genus Ceratognathus Westwood, 1838 1838. Entom. Mag., 5: 260-61.

Type Species (by original designation) : Ceratognathus niger Westwood. For the synonymy of this genus see Holloway (1961), pp. 61-62.

Ceratognathus passaliformis n.sp. Figs. 1-5.

Diagnosis. A small species, parallel-sided, dorsoventrally flattened, and with glossy black cuticle. Scales absent from dorsal surface of body. Apices of elytra and sides of pronotum prominently brimmed. Tibiae broadly spatulate. Sexual dimorphism very slight; sexes most readily distinguished externally by shape of distal margin of fifth abdominal sternite, which is uniformly convex in females, angulate in males.

Holotype Male

Length (with mandibles), 7.3 mm; (without mandibles), 6.9 mm: breadth, 2.5 mm.

Guticular surface uniformly densely and moderately finely punctate, except for pronotum which is smooth; puncturation of head slightly coarser than that of remainder of body. Punctures of dorsal surface with very fine, short, erect, pale setae; those of ventral surface with longer, coarser, subdecumbent, yellow setae.

Head short and broad, widest at the eyes; surface between eyes convex; anterior margin of head irregularly concave, with a prominent vertical rim; intermandibular projection short, very broad, and receding beneath anterior margin of head; preocular margin very short, obtusely angulate, and only slightly elevated above scape base; width of eyes together about one-fifth the total head width.

Labrum approximately vertical, triangular, and very sparsely setose. Mandibles small, arcuate laterally, shallow dorsoventrally; left mandible with a strong, simple, apical tooth, a small, ventral, subapical tooth and a small, dorsal, subapical tooth; right mandible with a large, apical tooth and a well-developed, dorsal, subapical tooth. Mentum with external surface smooth, sparsely setose and slightly convave; ligula composed of a small tuft of setae. Antennal club segments finely pubescent except for the opposing surfaces which are naked; club about 1.1 times wider than deep; scape very broad distally.

Pronotum about 1.2 times wider than long and about 1.7 times wider than head; disc flattened; front angles obtuse and not extending far forward: hind angles obtuse, not prominent; sides very irregularly and feebly serrated, approximately parallel on the posterior half, converging slightly anteriorly, and produced into a broad, horizontal brim.

Elytral shoulders rounded, not prominent; sutural margin not raised; apex of elytron with a broad, horizontal brim. Each elytron with about seven incomplete, longitudinal, shallow grooves.

Mesosternum slightly convex between second coxae. Metastemurn irregularly convex. Fifth abdominal sternite (Fig. 2) about 2.3 times wider than long; distal margin angulate in the middle.

Legs short, stout, and clothed with very fine, short setae. All tibiae flattened, broad, and very wide distally; anterior tibia with two large teeth and about 12 small, approximately equal-sized teeth along the outer edge. Tarsomeres short, sparsely setose. Arolium very small, almost completely concealed by fifth tarsomere.

Male Genitalia (Fig. 3). Aedeagus symmetrical. Proximal half of penis bulbous; distal half flattened from side to side, and blade-like, with the dorsal surface membranous in part. Ostium terminal and very small. Internal sac broad, with dense, brown spines on part of its wall. Parameres simple, blade-like, completely separated from basal piece, and articulating on dorsal side of basal piece.

Ninth abdominal segment (Fig. 4) symmetrical.

Allotype Female

Length (with mandibles), 7.0 mm; (without mandibles), 6.6 mm; breadth, 2.5 mm.

Differs from male in following characters: Sides of pronotum more prominently convergent anteriorly, and with a narrower brim. Fifth abdominal sternite about 2.5 times wider than long; distal margin uniformly convex.

Female Genitalia (Fig. 5). Bursal duct not distinct. Spermathecal duct (SD) opening into a large, weakly sclerotized, folded sac which may represent either the bursa copulatrix or the accessory gland, or perhaps a fusion of these two structures.

Type Material. Holotype 3, allotype $, and 11 paratypes are deposited in the collections of the Dominion Museum, New Zealand. Collecting details are as follows: Holotype $, at Jacob’s Ladder, Orongorongo Valley, near Wellington, New Zealand, 25.1.1961, B. A. Holloway. Allotype 5, same locality and date, R. G. Ordish. Paratypes: 3 3,3 $, same locality, 17.1.1961, D. Edwards and J. Balderson; 1 3,4 2, same locality, 25.1.1961, D. Edwards, R. G. Ordish and B. A. Holloway. All the specimens were collected in nests of Prolasius advena (Fr. Smith) under beech logs.

Variation. In some of the paratypes there is a small, ventral, subapical tooth on the right mandible. Measurements of the paratypes fall within the following ranges:

Length (with mandibles), 6.8-7.2; (without mandibles), 6.4-6.8 mm: breadth, 2.4-2.5 mm.

Distribution. C. passaliformis is known so far only from the type locality in the Wellington Province.

Taxonomic Note. The absence of scales on the dorsal surface of the body distinguishes C. passaliformis from all other known species of Ceratognathus in New Zealand. The male genitalia show most resemblance to those of C. helotoides Thomson (see Holloway, 1961) in that the parameres are simple and that the aedaegus and ninth abdominal segment are symmetrical. The female genitalia are similar to those of C. helotoides and C. cylindricus (Broun) in having the accessory gland and bursa copulatrix represented by a single structure. C. passaliformis bears a further resemblance to C. cylindricus in the apparent absence of sexual dimorphism of the head. In contrast, the tibiae of passaliformis differ markedly from those of both cylindricus and helotoides; in the latter two species the outer edge of the anterior tibia bears two large teeth and a small number of variably-sized teeth, whereas in passaliformis and the remaining New Zealand species of Ceratognathus there are two large teeth and numerous approximately equal-sized small teeth on the outer edge of this segment.

Biology. The type series was collected from two nests of Prolasius advena under decaying logs. Although the association of beetles and ants may have been accidental, there seems to be good evidence for assuming that C. passaliformis is a genuine myrmecophile. The beetles occurred in the galleries with the ants, and not merely in the rotten wood adjacent to the galleries. Also, a small lucanid larva probably belonging to C. passaliformis was found in a gallery of one nest.

Certain morphological features of the adults, such as the compressed and streamlined body, reduced vestiture, and paddle-like legs, suggest adaptation to a highly specialised type of existence, but the possible functional significance of some of these features in an ant-beetle relationship is not clear at the present time.

P. advena belongs to the Formicinae and is one of the few endemic ants of New Zealand (Brown, 1958). It is widespread throughout the North and South Islands.

Literature Cited

Brown, W. L., Jr., 1958. A review of the ants of New Zealand (Hymenoptera). Acta Hymenopt., 1 (1): 1-50.

Holloway, B. A., 1961. A Systematic Revision of the New Zealand Lucanidae (Insecta: Coleoptera). Dominion Museum Bull., 20.

Dr Beverley A. Holloway, Dominion Museum, Wellington, N.Z.