Art. XVI.—On Henops brunneus, Hutton.
[Read before the Wellington Philosophical Society, 11th January, 1888.]
Plate X., fig. 1-12.
About October last, a resident in the Wairarapa District sent down to the Colonial Museum a few twigs of apple, quite covered over with some black substance, amongst which were slowly crawling about half-a-dozen rather large flies; and he desired some information on this, which he considered as a new “blight,” stating that it occurred on both apple and peach trees in his garden. The specimens were referred to me; and at first sight I thought the sooty black coating to be the usual fungus accompanying scale-insects, the flies being unconnected with it. Closer examination, however, showed that the black mass was really composed of many thousands of eggs; and the flies were soon observed to be still laying more of these eggs on the twig, until in a short while it was so thickly covered with them as to be quite hidden. With the assistance of Mr. G. V. Hudson I found that the flies were undoubtedly Henops brunneus, a species of Dipteron hitherto only reported (in Hutton's “Catalogue of N.Z. Diptera”) from Lake Wanaka. I was able to assure the gentleman who sent the specimens that probably they would not do great harm to his trees.
But the investigation so far showed that the knowledge of Henops hitherto possessed was incomplete. The available works
in which it is mentioned were Hutton's “Catalogue” and West-wood's “Classification of Insects.” In the first, the description given is very short and indefinite: in the second it is stated that Henops and its allied genera are very little known, and “the larvæ have not been observed.” I placed one of the apple-twigs, covered with eggs, in a glass box, in the hope that the larvæ might possibly be hatched, and, after about five or six weeks, I found a perfect cloud of minute larvæ wriggling in the liveliest manner. Having thus achieved a further stage of knowledge of this species, and the fly itself being in some respects rather a curious one, I have ventured to bring forward the following description and illustrations of the larva and the imago. Unfortunately, not being able to procure a supply of apple or peach leaves, I have not succeeded in feeding the larvæ and obtaining pupæ. I tried various leaves as food for them, as well as giving them earth to burrow in, but they all died.
Family. Acroceridæ, Leach.
(Inflatæ, Latreille; Vesiculosæ, Macquart.)
Body short and thick; head bent down, small, entirely occupied by the eyes; thorax and abdomen large, inflated; proboscis variable, sometimes long, sometimes absent.
Genus Henops, Illiger.
Proboscis very short, scarcely noticeable; antennæ of two short joints with a long style. Eyes naked, compound. Abdomen broader than the thorax.
Henops brunneus, Hutton.
(Catal. of Dipt., 1881, p. 25.)
Flies (fig. 1) rather large, but squat-looking and heavy; motions very slow. Thorax much elevated, the head being bent down beneath it so as not to be visible when the insect is viewed from above. Abdomen round and swollen, wider than the thorax but seeming as if cut oft short, the posterior extremity being turned under; there are six segments on the abdomen.Colour dark brown, almost black, on the thorax, with short yellow hairs; abdomen dark brown, with a yellow band marking each segment; head black; wings hyaline; halteres yellow. The winglets are very large and scale-like. Eyes very large, compound, occupying all the upper part of the head, but not highly convex (fig. 2). Antennœ (fig. 3) inserted in front, between the eyes; two-jointed, both joints very short; the style is very long, inflated near the base, narrow in the shaft and
slightly dilated at the tip, where there are two short bristles. Proboscis (fig. 2) very short, almost obsolete, conical; placed so much beneath the down-turned head as to be extremely difficult to detect. Feet (fig. 5) long and slender; tarsus five-jointed; claw double (fig. 6) with three pulvilli. Wings (fig. 4) with brown costal and sub-costal veins; discoidal cell open; cubital cell large; the postical vein appears to have a branch almost if not quite disconnected. Length of the body, in the usual position, nearly ⅕, inch.
The eggs of this insect are very small, sooty black, truncato-ovate (fig. 7); as stated above, they are laid in such numbers as to cover a twig with a black coating.
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The larvæ are very minute, about 1/60 inch long; dark-grey or brown in colour; elongated, narrow, tapering at both ends, with twelve distinct segments, of which the fourth from the head is the widest; on each segment is a row of short fine hairs (fig. 8). They are in constant motion, wriggling: the mode of progression forwards is shown in fig. 9. The head is pointed and terminates in two very small hooks, with a pad or pulvillus (figs. 10 and 11). The posterior extremity is also acute, ending in three very minute points with, on each side, a thin curved appendage (fig. 12). The spiracles are only two, very minute circular orifices, situated on the last segment but one (fig. 12).
Both Mr. Hudson and I tried without success to procure the pupæ. The larva of a fly not far removed from Henops (Clitellaria) is said to take more than two years before undergoing its transformation.
In consideration of the fact that the larvæ of the whole family of Acroceridæ have not hitherto been known, and that the descriptions of the various genera are but fragmentary, the above account of Henops brunneus may be of interest. The larva would seem to be perhaps more similar to those of Cecidomyia than to any others of the order, though the perfect fly is quite different.
|Fig. 1.||Henops brunneus, flies on a twig, about natural size.|
|Fig. 2||" head of perfect fly, viewed from beneath||×||15|
|Fig. 3.||" antannæ of "||×||120|
|Fig. 4.||" wing of "||×||6|
|Fig. 5.||" foot of "||×||15|
|Fig. 6.||" claws and pulvilli of perfect fly||×||50|
|Fig. 7.||" eggs||×||15|
|Fig. 8.||" 109 larva||×||90|
|Fig. 9.||" larva, to show mode of progression.|
|Fig. 10.||" head of larva, viewed sideways||×||100|
|Fig. 11.||" " viewed from above||×||100|
|Fig. 12.||" last two segments of larva, showing spiracles||×||100|