HARDWICKE'S SCIENCE-GOSSIP. 



reference to the numerous nectar-secreting, insect- 

 attracting glands with which the leaf-stalk is 

 provided, and which are, perhaps, fully as interesting 

 to the student of Nature and as important in the 

 economy of the plant. 



I had been looking forward to this paper, scarce 

 doubting to see some reference to these singular, 

 and, so far as I am aware, almost, though not quite, 

 unique plant-organs in the British flora ; inasmuch 

 as they affect the habits and economy of one of Sir 

 John's favourite insects — the ant, and touch upon a 

 favourite and highly-interesting theme — the relations 

 of insects to plants ; and I must confess to being 

 somewhat disappointed at no reference being made 

 to the relations of the ant, as well as of a number of 

 other species of insects, to the common Guelder- 

 rose. 



It is a few years ago since I first observed and 

 closely attended to the habit of two species of our 

 ants freely and continuously haunting various species 

 of aphis-infested plants, for the purpose of milking 

 the Aphides,* i.e., obtaining the liquid anal excre- 

 tions of these insects— the so-called "honey-dew," 

 whose production most writers on Natural History 

 whose works I have read, assign to the two dorsal 

 cornua situate near the apex of the abdomen, but 

 which I have fully satisfied myself by repeated 

 and careful observations extending over a series of 

 years, is produced, so far as the Aphides are 

 concerned, by their anal emissions of liquid excreta, 

 and not by any emitted secretion or excretion from 

 the cornua ; and in the early summer of 1887 I first 

 became aware, by actual observation, of the habit of 

 these same two species of ants as freely and con- 

 tinuously affecting the bush vetch ( Vicia scpiimi) to 

 obtain the transparent sweet liquor — the nectar — so 

 plentifully secreted in the cavity on the under side of 

 the stipulas of the leaves cf this common hedge-side 

 plant, though on seeing it I at once remembered that 

 I had read of the circumstance in one of Grant Allen's 

 interesting and instructive Natural History books ; 

 but it was only about mid- June of last year (1888) 

 that I became aware of the fact of the same common 

 black ant (a species of Formica), as well as of other 

 species of insects, haunting the foliage of the 

 Guelder-rose for the purpose of revelling on the 

 abundant transparent sweet liquor secreted within 

 the hollow or trough at the summit of the numerous 

 elevated reniform green glands with which the leaf- 

 stalk at the base of the blade is furnished, and 

 which, running along each side of the channel in the 

 upper side of the stalk, not infrequently extend a 

 little distance up the blade of the leaf at one or both 

 sides, and sometimes, when very numerous, extending 

 to the base of the stalk and even on to the stipulas. 

 These glands are not invariably reniform, but may 

 be rounded, elliptical, or oblong. 



* SciENCE-Gossir, July, 1SS3, p. 150. 



On referring to my Natural History diary for 

 1888, I find, under date June nth, the following 

 first note bearing on the subject : At about 5 p.m. 

 this evening, as I was walking along a lane at 

 Killingworth, I discovered a low and somewhat 

 spreading bush of the common Guelder-rose 

 ( Viburnum Opulus) in the hedge-side ; and on 

 looking down upon its fresh and pleasing foliage, 

 found that it was swarming with the common black, 

 or rather, bronze-black, ant and a species of ant-fly 

 much resembling the ant, both in the form of its 

 thorax and abdomen and in its dark and bronzed 

 coloration. And what think you that they, as well 

 as many other small flies of at least two species, 

 were after ? Something that vividly recalled to my 

 mind Belt's "Naturalist in Nicaragua" account of 

 the acacia-inhabiting-and-protecting ant of Central 

 America ! They were visiting and sipping the 

 nectar from the kidney-shaped glands that exist on 

 the leaf-stalk at the base of the leaf of this small 

 tree or shrub ! Not infrequently two of the ants 

 were engaged at the same moment on the glands of 

 one leaf. The ant-flies ran about over the foliage 

 and up to the glands to sip ;the nectar, with the 

 wings, as is the habit of this tribe of Diptera, partly 

 raised and kept in perpetual motion, and the 

 abdomen raised and lowered a little incessantly — 

 kept palpitating, and, whenever an ant approached, 

 the fly took one of its short flying leaps to a respectful 

 distance from the — guardians (?) of the plant. 



All through the summer and autumn of iSSS, up 

 to the middle of September, I found the ant and ant- 

 fly invariably present on the foliage and at the 

 nectar-secreting glands ; also, on different occasions, 

 I observed other small flies, beetles, and moths, all 

 sipping the copiously secreted transparent sweet 

 liquor, 



This year (1889), so early as May 21st, before the 

 foliage was fully evolved, the ants were already up at 

 these leaf-stalk glands ; and all through the year, up 

 to October 4th, both the ants and ant-flies (which 

 appeared one week later) have been present, visiting 

 the glands, and lapping or sipping the nectar there- 

 from. Frequently, too, have I seen flies of several 

 different species, including the flesh-fly, dung-fly, and 

 flies of the size and type of the house-fly, and Ichneu- 

 mons of at least two species, obtaining the nectar ; as 

 well as on other occasions a medium-sized saw-fly, a 

 cynips, a spice-wife beetle (Tchphorus), a skipjack or 

 click-beetle (Alhous kamorrhoidalis), and also one of 

 the larger snipe-flies, the Empis tesselata. Notwith- 

 standing the long snipe-like tongue or proboscis of 

 the highly predatory Empis, which appears about as 

 suitable for lapping up the nectar from these leaf- 

 stalk glands of the Guelder-rose and the shallow 

 nectaries of many flowers, as the bill of the crane in 

 the fable, yet both it and many of its smaller con- 

 geners are frequent visitors to flowers for the sake of 

 the nectar; and when obtaining the sweet secretion 



