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Volume 40, 1907
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Art. XVIII.—Notes on the Destruction of Kumaras from the Friendly Islands (Tonga), caused by an Imported Weevil, with Descriptions of the Larva, Pupa, and Perfect Insect, &c.

By Major T. Broun, F.R.E.S.

[Read before the Auckland Institute, 12th December, 1907.]

Plate XXII.

During the years 1906 and 1907 I noticed numbers of imported kumaras that had been badly perforated by weevils, so several samples were secured and kept under observation in glass jars, in order that the perfect insect might be reared and identified. That operation was successful.

It was very desirable that that tedious process should be accomplished, because considerable quantities of kumaras might be illegally condemned by some experts of the Agricultural Department, who, no doubt, might imagine that the kumaras were infested with the potato-moth (Lita solanella), which belongs to an entirely different order of insects, and no more resembles the weevil than chalk resembles cheese. Indeed, one of the local importers assured me that such illegal condemnation had actually occurred.

Not only does this weevil attack kumaras, which is bad enough when potatoes are scarce and dear, but I have also reared it from island oranges. Here again the question of unauthorised condemnation arises, as the only prohibited insects are the Queensland fruit-fly (Tephrites tryoni) and the Mediterranean species (Halterophora capita); but another fly, discovered and described by me (Dacus xanthodes), which is just as destructive as the Queensland species, though found as far back as December, 1903, and afterwards reared in large numbers from island oranges, mammæ-apples, grenadillas, and more rarely from pineapples, has never been included in the schedule of the Orchard and Garden Pests Act.

The description of the fly (Dacus xanthodes) appeared on page 327, vol. xxxvii, of the “Transactions of the New Zealand Institute” for 1904, and also, what is more remarkable, on page 306 of the report of the Agricultural Department for the same year.

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Description of the Kumara-Weevil.

Cylas turcipennis, Shœnherr.

Generic Characters.

Body apterous, subcylindrical, transversely convex, medially constricted. Mandibles very short. Rostrum one-third shorter than thorax, cylindrical, moderately slender, subparallel. Scrobes antemedian, not visible above, forming deep oval cavities underneath and prolonged backwards as grooves extending to the eyes. Eyes longitudinally oval, lateral, finely faceted, distant from the thorax and each other. Thorax twice as long as broad, deeply constricted behind the middle, base and apex truncate, without ocular lobes. Scutellum absent. Elytra oviform but very elongate; shoulders much narrowed. Legs long; femora slender and stalk-like at the base, somewhat clavate towards the extremity; tibiæ unarmed. Tarsi elongate, 3rd joint deeply bilobed, with dense brush-like soles; between these soles the atrophied minute 4th joint may be detected; claws simple.

Anterior coxæ large and prominent, almost quite contiguous; intermediate globose, separated by the slender mesosternal process. Metasternum elongate. Abdomen elongate, the basal 2 segments of about equal length, their suture indistinct in the middle; 3rd and 4th short, with deep sutures; 5th slightly broader than long.

Male.—Antennæ not geniculate, composed of 9 joints; all of these are transverse, except the large basal joint, which is pyriform, but slender at the base. Club 1-jointed only, cylindrical, nearly twice the length of the preceding 9 joints combined, finely asperate and pilose.

Female.—Antennal articulations 2 to 9 of the funiculus are each longer than those of the male, obconical. Club elongateoval, similarly pubescent, but only about half as long as that of the other sex.

Obs.—Lacordaire terms the basal joint of the antennæ the scape, giving 8 joints to the funiculus, but as the antennæ are not elbowed I have described them as 9-articulate, with the additional 1-jointed club.

Specific Description.

Elongate, shining; elytra blue; head and rostrum darker; thorax red; legs infuscate red; antennæ nigrescent, but with the club and the base of the 1st joint reddish.

Rostrum moderately slender, finely and distantly punctured rather more closely near the apex. Head slightly and gradually

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narrowed anteriorly, with very few minute punctures, the interocular space rather dull and feebly bi-impressed. Thorax convex, nearly twice as long as it is broad, behind the middle deeply and widely constricted, its basal portion evidently narrower than the laterally rounded frontal part, its surface smooth, there being only a few minute punctures. Elytra more than twice as long as they are wide, rather wider near the middle than the thorax, much narrowed posteriorly; they bear several series of minute punctures, in each of these there is a very small inconspicuous grey seta. Legs finely setose; tibiæ slightly flexuous, and thickened at the extremity; tarsi pilose above.

Under-side transversely convex. Prosternum somewhat incurved in front. Metasternum and ventral segments dark-blue, the coxæ and mesosternum reddish, sometimes other parts are refescent. The short 3rd and 4th segments are densely and minutely sculptured. The general sculpture and clothing are much like those of the dorsum.

Length, rost. incl., 3 ¼ lines; breadth, ⅝ line.

Description of the Larva.

Length, 3 lines; breadth, ¾ line.

Cylindrical, with a tendency to become a little arched; 3rd, 4th, and 5th segments just perceptibly broader than the others. The head, 1st segment, rather small, nearly circular, with a fine longitudinal central groove, but without other definite sculpture. Mandibles short and inconspicuous, dark-brown. Trophi small.

Along the back there is an ill-defined linear impression between the 3rd and 10th segments. The 2nd and 13th segments are not well delimited, but between the others there are contractions, so that the side of each of these appears prominent and rounded. The surface is minutely shagreened and more or less uneven, below as well as above, but not distinctly punctate, and there are only a few short greyish setæ visible.

No eyes or legs are perceptible; these latter, however, are represented underneath on the sternal segments in front by smooth nodosities.

In the kumara itself the larvæ are nearly white, but become of a pale brownish-red after immersion in formalin and water.

Description of the Pupa.

Length, 2 ½ lines.

Colour similar to that of the larva. When viewed from above, the frontal portion of the prothorax is seen to bear 6 minute tubercles, 2 in front and 2 at each side; from each of these a moderately distinct and rather long seta arises.

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The lateral prominences near the front represent the bent 4 anterior legs and the antennæ; the posterior pair of legs are apparent below. The elytra follow; these are obviously grooved; the grooves converge and unite by pairs before reaching the extremity. The rudimentary wings appear below the elytra, and are situated closer to the sides of the body, but they are destitute of striæ.

Hind-body with apparently 9 segments, the basal largest and broadly grooved along the middle, the terminal somewhat transparent and provided with 2 flexuous appendages, 1 at each side of the extremity.

Under-side shining. Immature specimens exhibit the head and rostrum, but the former shows no indication of eyes. In a more advanced stage the black eyes and claws of the tarsi, as well as the fuscous mandibles, are quite easily distinguishable under a good lens.

All the preceding descriptions have been taken from specimens reared by me at Auckland.

The attached illustrations were kindly executed by Mr. D. W. Jones, the head teacher of Papakura School.

Explanation of Plate XXII.

Fig. 1. Cylas turcipennis, male.

Fig. 2. Cylas turcipennis, female.

Fig. 3. Section of damaged kumara. The dark spots show the cavities made by the larvæ

Fig. 4. Larva.

Fig. 5. Pupa.

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