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Fam. Syrphidæ (Hover-flies).
The members of this family are both large and small, and are beautifully coloured with yellow and green. They are usually found hovering over flowers in the sun, and can be recognised by their mode of flight alone, which is described thus by Kirby: “They hover motionless in the air, and, if alarmed, dart off with a rapid motion that the eye cannot follow, and hover again as soon as they stay their course.”* The larvæ are beneficial to gardeners, as they destroy large numbers of injurious insects.
Eristalis tenax (introduced).
Abundant everywhere from February to March; also found—but in decreasing numbers—in April and May. This species is found hovering about flowers in the sun. When it alights, the abdomen may often be seen moving up and down, and the wings are held in such a position as to expose the abdomen. I observed a specimen feeding on the pollen of a dandelion: the fly took hold of the stamen of a flower with its proboscis—which appears to be bifid at the distal extremity—and passed it once or twice up and down the stamen in order to rub off the pollen. After this operation had been indulged in two or three times, the fly held out its proboscis at full length, and moved the bifid portion as if it were in the act of tasting. Another specimen I observed to rest on the broken end of a holly-twig, by alighting so that the sharp edge of the broken twig came between the bases of the fore and middle legs; the fly steadied itself with the posteriortarsi pressed against the sides of the twig, while it cleaned its fore tarsi and proboscis; the middle legs meanwhile were outstretched. This specimen remained thus for about four minutes.
Helophilus trilineatus. (Plate XXIX, fig. 5.)
Not very common. I captured one specimen at Taieri Mouth in January (1908) as it alighted on a blade of grass in the sun. At Roslyn, during February of the same year, two were obtained resting on a marigold-flower exposed to the sun.
Helophilus antipodus.
Found at Roslyn, November (1908). I captured this species amongst some long grass in the sun, the day being very warm. A large number were observed hovering over a stream on Mount Cargill during February
[Footnote] * I have lately observed a distinct difference between the flight of S. novœ-zealandiœ and that of M. fasciatum: the movement of the former being jerky contrasted with the gliding motion of the latter.
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(1909), and in the same month, as well as in March, several were captured on the hills of Purakanui. H. antipodus produces, during flight, a humming sound like that of a bee, but of a more acute tone.
Helophilus ineptus.
Common at Roslyn during February and March (1909). One very hot and sunny day in January I captured this fly on the banks of a small stream above Murdering Beach.
Helophilus chathamensis.
There is no record of this fly having been found before in New Zealand, since Captain Hutton's specimens were captured at the Chatham Islands. I found an individual on the sea-shore of Taieri Mouth, where it had been blown by a strong wind, in January (1908), and the following month I captured another hovering above a clump of marigold-flowers at Roslyn. On a small cliff at Tomahawk, during October (1908), a large number were taken while at rest on or hovering over some wild flowers attached to the rock; at the foot of this cliff a stream runs into the sea.
Helophilus latifrons.
Captured on a hillside near the bush at Taieri Mouth, December (1907). Two specimens were obtained at Roslyn during September (1908), and two more from Tomahawk in the following month.
Syrphus novæ-zealandiæ. (Plate XXIX, fig. 1.)
One of the most abundant of New Zealand Syrphids: it is to be found everywhere during the season, appearing about September and becoming less common in April; only a few are to be seen during May, and then only in sunny weather. This species varies greatly in colour, the yellow being in some a deep in others a very light shade, and may even be tinged with green. If a specimen be captured shortly after it has emerged from the pupa, the yellow spots are transparent, the black colour transmits the light, and thus the organs contained in the abdomen are rendered visible. I kept two specimens in confinement—a male and a female—for a few days. The male flew about more than the female, the latter feeding, most of the time, on the pollen of daisies which I had put in for food. These observations were made during May (1909), at which period the weather was becoming cold, so that the Syrphids were inert; but on the application of a little warmth they immediately showed signs of returning animation—the female returned to the flowers, while the male amused itself by endeavouring to find an exit. After a few minutes the female would stop feeding and stretch out the proboscis to its full length; this action having been accomplished once or twice, feeding was resumed; occasionally the fly would rub the proboscis with the fore tarsi. When this species alights, the wings are either held outstretched or folded over the abdomen, which is frequently kept in motion, as in E. tenax. On a drop of nitric acid being held about a quarter of an inch from the antennæ of a female, the fly immediately started back or dodged from side to side, endeavouring to avoid the acid; when held at the side of the thorax the acid did not appear to affect the specimen.
Syrphus ortas. (Plate XXIX, fig. 2.)
This species is rare. I have found only one specimen, which was resting on a dandelion exposed to the sun—Roslyn, September (1908).
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Melanostoma fasciatum. (Plate XXIX, fig. 3.)
Common; usually to be observed from January to April. I found no specimens at Taieri Mouth at the beginning of 1907, but they were abundant at and round about Dunedin during January 1908. A large number were captured amongst long grass and upon rushes growing in swamp exposed to the sun.