Art. IV.—On the New Zealand Cicadæ.
[Read before the Wellington Philosophical Society, 23rd July, 1890.]
Probably few groups of insects are so well known and yet so little understood as the Cicadæ. These creatures are generally called “singers,” and are familiar to nearly every New Zealand child, but at present entomologists appear to have somewhat neglected them. They are also frequently spoken of as “locusts,” which is an extremely misleading name, and should be at once dropped. Professor Westwood has long ago pointed out that the term “locust” should only be applied to that group of the saltatorial Orthoptera having short erect antennæ, of which the migratory locust (Locusta migratoria) may be fairly taken as a type; but, unfortunately, this excellent definition has not been adhered to, even by professed naturalists.
The Cicadæ belong to the order Hemiptera, group Homoptera, and may be easily recognised by the following characters:—
The head is short, broad, and transverse, with large prominent eyes; the ocelli, three in number, are placed on the back of the head in a triangle; the face has a large, nearly circular, swollen, and transversely-striated piece, close to which, at the upper angles, and between the eyes, the antennæ are inserted; these are apparently composed of seven joints, the basal joint being thick and the others slender, and gradually attenuated to the tip. The rostrum, promuscis, or, more strictly speaking, the labium, is greatly elongated and three-jointed; the basal joint being very short, and the terminal joint very long and slender; the mandibles and maxillæ are represented by four fine setæ passing through the promuscis, and the palpi are entirely wanting. The prothorax is short and transverse, the mesothorax
very large, the metathorax scarcely visible above, except at the sides; beneath, these segments are nearly equal. The abdomen is short and somewhat triangular; the legs are short, the anterior femora thickened and toothed beneath; the posterior tibiæ slightly spined, without terminal spurs. The tarsi are three-jointed. The forewings are large and rather narrow, deflexed at the sides of the body, and of a uniform consistence, with comparatively few and very distinct veins.
It may perhaps be of some interest to mention here that only a single and very rare species of Cicada (C. anglica, Curt.) is found in the British Islands, but as we go southwards on the European Continent Cicadæ of various species become common, showing that they are essentially insects of a sunny and warm climate like our own.
Of the New Zealand species of Cicada at present known to me, two are already described and four are new; but, as my observations have been practically limited to the shores of Cook Strait, it is highly probable that several other species will be discovered in the future. I will begin by describing Cicada cingulata, Fabr., which is the commonest and most conspicuous species, and will then briefly point out the characters by which the others may be recognised.
Cicada cingulata, Fabr.
Head and thorax dull-green, with black markings. There are two ill-defined black streaks in the neighbourhood of the ocelli, which last are brilliant crimson, like rubies set in the forehead of the insect. Prothorax with two black stripes in the centre, enclosing a space which appears as a broad central band; depressions black; margin green. Mesothorax with two central and two lateral conical black markings, the bases of the cones being directed towards the hind margin of the prothorax. Abdomen black, with the margins of the segments dull-red. Fore-legs green, with two black stripes and dots on the femora; tip of tibia and tarsus black. Middle-and hind-legs pale-green, basal joints of tarsi and tips of tibiæ black. Underneath the insect is dull ochreous-brown, with much fine silvery hair, which is also occasionally present on the upper sides of the abdomen. The female differs in being redder in colour on the abdomen, which is also ornamented with two broad black stripes on each side of the last segment. The penultimate segment is entirely free from all markings, and usually paler in colour than the rest. Wings with the basal space green, the costa and primary veins being brown, and the others black. There is a black dot at the anal angle of the hindwing, and two black dots on the costa of the forewing near the tip.
The females of all the species of Cicadæ may be at once known by the presence of a short ovipositor (Pl; IX., fig. 3, c) which is used for drilling into the stems of plants when they deposit their eggs; and the males by the existence of two peculiar drum-like organs, attached to the metasternum and covering two large chambers situated in the basal segment of the abdomen. These cavities contain two stretched membranes acted upon by powerful muscles, and instrumental in producing the noise for which these insects are so justly celebrated. (See figs. 2 and 3, which represent the under-surface of the body in ♂ and ♀ Cicadæ) This insect (C. cingulata) varies considerably in size and colour, some specimens being quite ochreous in place of green; but it can always be easily distinguished by its large size. Length of the body, 11 to 12 lines; expanse of wings, 32 to 37 lines.
The song of this Cicada is very loud, and rather harsh. It is capable of considerable modulation, and each rhythm consists of three or four notes. The insect usually, however, gives three chirps, then a pause, and three more, keeping this up for five or ten minutes at a time, and perpetually varying the rate of the music.
α. var. obscura.—I know of only one distinct variety of this species, which is remarkable for its smaller size, dull colour, and very loud chattering song. It is found among the boulders in the river-beds near the Inland Kaikoura Mountains; but I do not think it is any thing more than a variety.
Cicada cingulata first appears about December, and gradually increases in numbers till the middle or end of February, when in certain localities its singing is almost deafening. Occasionally trees may be seen swarming with these insects, which delight to rest on the branches in the hottest sunshine. A sharp hand is needed to effect a capture, even with a net, as the insects lose no time in making off when once they stop singing. This occurs on the approach of any enemy, and is no doubt taken as a danger-signal by the otherCicadæ. The ordinary house-sparrow destroys enormous numbers of this fine insect, and I do not think it will long remain abundant in the neighbourhood of our larger towns. In fact, even during the last seven years the species has become decidedly scarcer in the Wellington gardens.
Cicada muta, Fabr.
This species differs from Cicada cingulata in the following respects: The body is slightly more attenuated. There is always a distinct silvery stripe down the centre of the abdomen, and an ochreous stripe margined with black down the centre of the prothorax. No general description is possible, owing to the remarkable variations to which the insect is subject, but
the following is a table of the varieties that have at present come under my notice
α. var.sub-alpina.—Dark-green, with black markings consisting of two broad stripes on the inner margins of the eyes; two stripes in the depressions on the prothorax; two small central, and two elongate lateral, cone-shaped markings on the meso-thorax; a broad band on each side of the central silvery stripe on the abdomen, and two small stripes on each side of the posterior segment in the female. Wings tinged with green, veins green, costa red, legs green, with black tips to all the joints. This variety frequents forest-clad hills, and is taken abundantly as far up as 4,000ft., when it is replaced by C. cassiope. presently to be noticed. It is undoubtedly one of the most abundant varieties of C. muta.
β. Var rufescens.—Reddish-ochreous, with black markings as in var.α, except that the sides of the abdomen are frequently much suffused with black. Wings clear, with reddish veins. Many of the females of this variety are very pale in colour, becoming, in fact, quite ochreous. Common in the Maitai Valley, Nelson.
γ. var. flavescens.—Of this form I have but one specimen, which was taken on the lower slopes (3,500ft.) of Mount Tapuaewaeonuku, and is quite a bright-yellow colour. It is a female, and must be regarded more as an extreme form of rufescens than as a distinct variety.
δ. var.cinerescens.—In this form the black markings are much suffused on a dull brownish-yellow ground. The central stripe is, however, present throughout the whole of the insect, and is consequently very conspicuous; veins dull-brown. This variety is very common in the Wairarapa and Wellington districts.
ç. var.minor.—Distinguished by its small size, shrill song red basal portions to the wings, black suffusion of mesothorax, and silvery pubescence. Common among the coarse native grasses growing on sandy ground just above high-water mark, Wellington, and in similar situations on the banks of the Manawatu River, near Palmerston North. Of this variety I have at present only taken male specimens.
Cicada muta varies in length of body from 7 to 11 lines; expanse of wings, 16 to 25 lines.
Cicada tristis, n.s.
This species is at once recognised by its elongate wings and parallel-sided body, the head being the broadest part of the insect, In colour it is bronzy-green, covered with fine silvery hair, and occasionally a central silvery stripe on the abdomen. The markings are dull brick-red, margined with black, and consist of an irregular blotch covering the whole of the top of
the head; two broad bands on each side of the prothorax, leaving the margins and a central stripe green; and a broad red stripe on the posterior margin of each of the segments of the abdomen. Wings tinged with brown, veins brown, costa reddish, a blackish suffusion in the anal angle. Length of body, 8 to 9 lines; expanse of wings, 22 to 24 lines. This curious and interesting species occurs on the forest-clad hills around Wellington during February, March, and April. It may be known by its sad and exceedingly feeble song, which may be often heard on a cold autumn afternoon long after all other signs of insect-life have vanished.
Cicada aprilina, n.s.
This is certainly the most beautiful of the New Zealand Cicadæ. Its colour is a uniform bright-green, of a most striking intensity when alive. It has no markings on the prothorax; but there is a very obscure blackish line round the ocelli, and two fine longitudinal black lines near the centre of the mesothorax. The abdomen has a central silvery stripe, occasionally margined which black, but otherwise the insect is entirely destitute of any markings. Legs and wing-veins bright-green, except tarsi and inner marginal vein of forewings, which are crimson. Length of body, 8 ½ lines; expanse of wings, 22 to 24 lines.
This species first appears about the middle of February; but is most abundant in April. Its song is very quick and shrill, and is instantly hushed on the approach of an enemy. This Cicada is, in fact, extremely wary, flying off for a great distance when disturbed. Its green colouring is also highly protective, and renders the insect excessively hard to see amongst foliage. These peculiarities probably result from the circumstance that the insect appears late in the year, when few other species are about, and thus it has been much sought after by insectivorous birds, protective coloration and extreme caution being naturally the result of the “survival of the fittest.” I have not noticed this species anywhere but in the Botanical Gardens; but there it is tolerably common, although very hard to obtain—in fact, it is only to be captured by approaching very quietly and slowly, and then suddenly striking with the net as soon as the insect is detected.
Cicada iolanthe, n.s.
This is the smallest species of Cicada with which I am at present acquainted. In colour it is dark greenish-black, with the edges of the segments reddish-brown, but the female is often much suffused with brown. There are no distinct markings in eigther sex. The wings are very broad and short in
proportion to the body, which is more stoutly built than in any of the species we have previously considered. Length of the body, 6 to 6 ½ lines; expanse of wings, 12 to 14 lines. This Cicada first appears about November, but is somewhat rare. It may be at once known by its extremely shrill song, which is not so rapid in its rhythms as that of Cicada aprilina.
Cicada cassiope, n.s.
This is the alpineCicada of New Zealand, and has occurred on the mountains in the Nelson and Marlborough Provinces at elevations ranging from 3,000ft. to 5,000ft. In colour the male is nearly black, with the thoracic markings faintly indicated. The veins of the wings are also black. The female differs in being densely covered with dull-whitish hair. The wing-ribs are often pale-brown, but occasionally black, as in the male. Length of body, 9 to 10 lines; expanse of wings, 19 to 22 lines. This species delights to bask in the hot sun shine amongst the rocks and shingle on the mountain-tops. Its note is very weak and shrill, resembling in its slow monotonous character that of C. tristis. It is fairly abundant where found, but, like all the other Cicada, it is not by any means an easy victim to the net.
These two species(Cicada iolanthe and C. cassiope) are evidently very closely allied, but I think they are sufficiently distinct to be regarded as species in the ordinary sense of the word.
Respecting the life-histories of these beautiful insects, I can at present supply very little information.
The larvæ are occasionally found in the earth during the spring and winter months. They are generally supposed to feed on the roots of plants, but, judging from the fore-legs,. which appear to be raptorial as well as fossorial in their structure, it would seem quite possible that they are carnivorous, feeding, perhaps, on the juices of other insects, which they might readily imbibe through their long cylindrical proboscis.
The pupæ (fig. 9) differ chiefly in having rudimentary wings (PP), the legs, &c, being of course more perfectly developed than in the larvæ. When mature, this pupa works its way to the surface of the ground, ascending the stem of a tree, and firmly clinging on by its tarsal claws. The skin on the back of the thorax now splits open, allowing the enclosed Cicada to escape. Here the insect rests for a time, until the wings are sufficiently hardened, when it flies away. Numbers of these empty pupa-shells, or exuviæ, are constantly to be seen attached to the stems of trees in the forest, where they always remain until dislodged by some accident.
The alleged occurrence of the well-known Mole-cricket (Gryllotalpa vulgaris) in various parts of New Zealand has in some instances been probably due to the observation of a Cicada pupa, which, when alive and partially covered with earth, might readily be mistaken for the larva of that insect, although, of course, in reality it has no manner of affinity with it.
In conclusion, I will give a brief summary of the leading characters of the New Zealand Cicadæ:—
A. Cicadæ with a median band.
1. On prothorax only.
C. cingulata, Fabr.
2. On thorax and abdomen, very strongly pronounced. Very variable—green, black, red, and yellow, with black markings.
C. muta, Fabr.
3. With median band faintly indicated both on thorax and abdomen, bronzy-green, with reddish-brown markings. Constant.
C. tristis, n.s.
4. Entirely green, with median band on abdomen only, and two minute black markings on thorax. CońsAtant.
C. aprilina, n.s.
B. Cicadæ without median band.
5. Small, with no distinct markings. Constant.
C. iolanthe, n.s.
6. Larger, with thoracic markings faintly indicated. covered with greyish down. Constant.
C. cassiope, n. s.
Explanation of Plate IX.
Fig.1.Cicada cingulata, considerably enlarged, showing typical markings, general structure, and neuration, which last is absolutely identical in all the six species.
Fig.2.Under-side of abdomen of ♂ Cicada, showing the vocal drums, or opercula (b b): a a, coxæ of posterior legs; M, metathorax; 1 to 6, segments of abdomen. (Enlarged.)
Fig. 3.Ditto in the ♀: b b, rudiments of the opercula of ♂; the ovipositor; the rest as in fig. 2. (Enlarged.)
Fig. 4. Antennæ of mature Cicada. (Much magnified.)
Fig. 5. Antennæ of pupa. (Much magnified.)
Fig. 7. Fore- and (6.) hind- or intermediate leg of Cicada: a, coxa; b, trochanter; c, femur; d, tibia; e, the 3-jointed tarsus. (Enlarged.)
Fig. 8. Head of Cicada seen from the front: s s s, the ocelli; c c, the compound eyes; a a, the antennæ; p, the promuscis, or rostrum. (Enlarged.)
Fig. 9. Pupa of C. cingulata: p, the promuscis; T1, prothorax; T2, mesothorax; T3, metathorax; P P, the wing-cases. (Slightly enlarged.)