ret 7/76 f<5! I HARVARD UNIVERSITY LIBRARY OF THE Museum of Comparative Zoology £ J). £1,1$. 1iT VOL. 13 MAY 1 -1 :'JJ3 4 Transactions OF THE Society for British Entomology World List abbreviation: Trans. Soc. Brit. Ent. EDITED BY E. J. POPHAM, D.Sc., Ph.D., A.R.C.S., F.R.E.S. WITH THE ASSISTANCE OF W. A. F. BALFOUR-BROWNE, M.A., F.R.S.E., F.L.S., F.Z.S., F.R.E.S., F.S.B.E. W. D. HINCKS, D.Sc., F.R.E.S. B. M. HOBBY, M.A., D.Phil., F.R.E.S. G. J. KERRICH, M.A., F.L.S., F.R.E.S. O. W. RICHARDS, M.A., D.Sc., F.R.E.S., F.S.B.E. W. H. T. TAMS Date of Publication: 30th April, 1958 Copies may be purchased from the Publications Secretary, Department of Entomology, The Museum, Manchester, 13 Price 5s. od. post free Published for the Society by the British Trust for Entomology Ltd. BRITISH TRUST FOR ENTOMOLOGY LTD. 41 QUEEN’S GATE, LONDON, S.W.7 OFFICERS AND COUNCIL OF MANAGEMENT, 1958-9 Chairman: C. W. MACKWORTH PRAED, F.R.E.S. Hon. Secretary : N. D. RILEY, C.B.E., F.Z.S., F.R.E.S. 41 Queen’s Gate, London, S.W.7 Assistant Hon. Secretary {Finances): H, N. MICHAELIS 10 Didsbury Park, Manchester 20 Hon. Editor: E. J. POPHAM, D.Sc., Ph.D., A.R.C.S., F.R.E.S. Department of Zoology, The University, Manchester 13 Other Members of Council of Management of the Trust: J. E. COLLIN, J.P., F.R.E.S. B. M. HOBBY, M.A., D.Ph. R. W. LLOYD, F.R.E.S. SHEFFIELD AIREY NEAVE, C.M.G., O.B.E., D.Sc. T. H. C. TAYLOR, D.Sc. Professor G. C. VARLEY, M.A., Ph.D. W. D. HINCKS, D.Sc., F.R.E.S. G. S. KLOET, M.Sc., F.R.E.S., F.Z.S. All official correspondence should he sent to the Secretary of the Trust ItUK - - ~; Luis 1 i ; yims , . y 1 TRANSACTIONS OF THE S O C 1 ET-Y— ' FOR BRITISH ENTOMOLOGY Vol. 13 30th April, 1958 Part 4 Notes on the identification of Limnophila larvae (Diptera-T ipulidae) Part i By Allan Brindle, F.R.E.S. A number of the larvae of this genus have been described by various authors, but the descriptions are scattered in many publications, and some descriptions are without figures or otherwise inadequate for the separation of species. It is the aim of this series to describe and figure relevant parts of the larvae in order to assist identification. As far as possible characters will be used which are readily recognizable — this will enable certain species of larvae to be identified in the field. Some species, however, are so similar that characters requiring microscopic examination are needed to separate them. In the larvae of the genus Tipula most of the larvae can be separated by macroscopic characters, but in the genus Limnophila these have a limited application. As a preliminary it is proposed in this paper to describe and figure the anal segments of one species of larvae from each of the subgenera Phylidorea , Elaeophila , Limnophila , and Pseudolimnophila, and two species of larvae from the subgenus Pilaria. The larvae of the genus Limnophila are cylindrical, tapering anteriorly, and truncate posteriorly; usually carnivorous, very active, and live in moist or wet soil, or debris, into which they burrow quickly. The colour varies, even in the same species of larvae, from brownish to yellow or whitish, though yellow is the prevailing colour. A covering of fine, soft, short pubescence occurs on the body, in some species of larvae being so thick as to give a silky or iridescent appearance; in others being more scanty, and in the larvae of L. maculata (Mg.) this pubescence is so scanty and the cuticle so transparent as to allow the gut contents to be clearly seen. The larvae possess slightly developed welts on the ventral surface to assist progression. A characteristic feature, but one which is not confined to this genus, is the inflation, at times, of the penultimate segment, which, according to Crisp and Lloyd (1954) alfords anchorage in mud. This swelling of the penultimate segment often occurs during preservation, and this is shown in the drawings of L. lineola (Mg.), L. verralli (Bergr.) and L. discicollis (Mg.). A4 5« 1 [April The anal segment is truncate posteriorly, possessing a spiracular disc with two spiracles. The spiracular disc is bare and shiny, and coated with a secretion of the perispiracular glands (Keilin, 1913, 1944). The disc is surrounded by four or five lobes — two ventral, two lateral, and, when present, a fifth dorsal lobe. The dorsal lobe is always small when present, and appears to be present only in the larvae possessing an anal segment of generalized or primitive type. Fig. 2 illustrates an anal segment of this type. The lobes appear to serve an accessory respiratory function — that of containing a supply of air when the larva burrows, or assisting buoyancy when the larva reaches a water surface, when the lobes can be spread out to allow the spiracles free access to air. The long pointed lobes of Elaeophila or the elongated ventral lobes of Pseudolimnophila perform the same function, aided by the marginal hairs which are very long in the latter genus. In the larvae included in this paper the marginal hairs are very short in Limnophila ( Pilaria ) nemoralis (Mg.). In this case the lobes are capable of being folded down their mid-line, forming a cup in which air can be contained. In Limnophila (. Limnophila ) punctata (Schr.) they are much longer, but are still more or less of equal length. Further development tends to concentrate the longer hairs around each of the four lobes, the ventral lobe becoming the larger, with a correspondingly larger and longer array of hairs. In the two most developed forms included here, Limnophila ( Pilaria ) discicollis (Mg.) and L. (. Pseudolimnophila ) lucorum (Mg.) the former has very long hairs concen¬ trated at the tip of the ventral lobes (fig. 21), whilst in the latter case equally long hairs occur around almost the entire edges of the ventral lobes (fig. 17). Ventrally, towards the posterior of the larvae, are four anal papillae, arranged in the form of a cross, in the centre of which lies the anus. It is assumed these papillae perform an osmo-regulatory function, and, as in the genus Tipula , some correlation can be noted between the water content of the habitat and the size of the papillae, the larvae living in wetter conditions having longer papillae. The head capsule of the larvae of the genus shows considerable variation, ranging from the massive capsule of Pseudolimnophila to the greatly dissected type of Elaeophila. It can be noted that the degree of dissection of the head capsule cannot be correlated entirely with the present classification of the genus, nor can it be satisfactorily correlated with the anal segment. The subgenus Elaeophila , however, is a noteworthy exception. It is intended in the present series to use the characters of the anal segment to separate the species as far as possible. Further distinctions may be made using the characters of the head capsule. 1958] 59 The development of the anal lobes from the generalized type in figs. 2 and 6 appears to follow two distinct trends. In one, the two lateral and two ventral lobes are elongated into long pointed processes, as in all the Elaeophila larvae (figs. 13, 14, 15). In the second trend, the ventral lobe has been elongated only, with the lateral lobe remaining small (figs. 9, 16, 20). This reaches a climax in fig. 16, where the ventral lobes are very long and heavily sclerotized on the upper surface. In both these trends the dorsal lobe is suppressed. The pupae of the genus often show a remarkable power of movement. This feature is shared with the pupae of the genus Tipula which move upwards through the soil by means of their spines prior to emergence of the adults. The pupae of Limnophila ( Pseudolimnophila ) lucorum (Mg.), however, actually moved up the vertical glass sides of a jar for some two inches before the adults emerged. The same feature has been noted with occasional pupae of Limnophila ( Phylidorea ) lineola (Mg.). The larvae have been obtained by three methods : by orthodichlorbenzene technique, by sieving, and by flotation. The use of the first is risky as the larvae are soon adversely affected if the solution is at all strong. Sieving is rapid but is restricted to the neighbourhood of free water. A sieve of about 10 inches in diameter with a mesh of 16 to the inch has been used. This mesh is large and allows the larvae to creep through the mesh unless the sieving is done quickly, but in practice it is the smallest mesh which can deal with a fair variety of soil textures, and good numbers of the larvae can be obtained. Flotation is excellent but difficult to perform in the field, necessitating transport of soil samples which may contain few or no larvae. A combination of the last two methods seems to work reasonably well — sieving to find good samples and the subsequent flotation of these. The larvae have been reared by separating the species under a hand lens, preserving a small sample, and rearing each species of larvae in separate groups, and by rearing individuals in isolation. The latter method serves as a useful check on the first method, since the exuviae can usually be recovered, after pupation or after the emergence of the adults. In practice it is often found possible to obtain numerous larvae in separate species groups, depend¬ ing on the type of soil investigated, and the time of year. The larvae to be preserved have been killed by immersion in hot (6o° C.) water followed by preservation in Pampel’s fluid. The drawings illustrating this paper have been made from these preserved larvae using a camera lucida. B4 6o 4 [April Details of the marginal hairs have only been included in the posterior view (except in figs. 9, 12) in order to give the drawings sufficient clarity, but descriptions are included in the particular larval description. It will be noted that the figure of the anal segment of Limnophila ( Pilaria ) discicollis (Mg.), fig. 21, does not entirely agree with the one from Gerbig (1913) shown in Alexander (1920), fig. 232. The present figure has been checked with a number of preserved larvae and seems to be constant. A key is provided for the separation of the six species of larvae described here, and this will be extended in future papers, when comparisons will be given for the separation of other species of larvae. Larval Key 1 (2). Anal papillae longer than width of anal segment (fig. 18); ventral lobes parallel sided and heavily sclerotized on the upper surface (figs. 16, 17) . Pseudolimnophila lucorum (Mg.)* 2 (1). Anal papillae shorter than width of anal segment; ventral lobes shorter and not entirely sclerotized. 3 (6). Anal papillae twice as long as broad, broad at base, tapering towards tip (figs. 3, 22). 4 (5). The four lobes of spiracular disc subequal; dorsal lobe present (fig. 2) . Limnophila punctata (Schr.) 5 (4). Ventral lobes of spiracular disc much longer than lateral lobes; dorsal lobe absent (fig. 20) . Pilaria discicollis (Mg.) 6 (3). Anal papillae small, ovoid (figs. 7, 11, 15). 7 (8). Four lobes of spiracular disc elongated into long pointed processes (figs. 13, 14, 15) . Elaeophila verralli (Bergr.)* 8 (7). Lobes of disc not long and pointed. 9 (10). The four lobes of disc subequal; dorsal lobe present (fig. 6) . . Pilaria nemoralis (Mg.) 10 (9). Ventral lobes of disc longer than lateral lobes; dorsal lobe absent (fig. 9) . Phylidorea lineola (Mg.) The larvae of the above six species are described in the present paper. The structure of the anal segment of Limnophila (P.) meigeni Verr.,* closely resembles that of L. (P.) lineola (Mg.). In practice these larvae inhabit totally different habitats, so a larvae resembling lineola from peaty soil will be meigeni. On the other hand, another species of Phylidorea , L. (P.) fulvonervosa C Schum .) appears to have a larvae more resembling L. (P.) discicollis (Mg.). The differences between these larvae will be included in the second part of this series. 1958] 6i The structure of all the Elaeophila larvae is identical. L. (E.) mundata (Loew) appears to be a doubtful species (Coe et al. (1950)), and the larvae of L. (E.) trimaculata (Zett.),* verralli (Bergr.),* apicata (Loew),* maculata (Mg.),* and submarmorata (Verr.) have been bred by myself during the past few years. All are closely similar though it has been found that they can be An.pl -secjmeats L^nophilo. ^o«-vo t P- unc tatcv. ( Schr) partially (and tentatively) separated on macroscopic characters. Thus the larvae of submarmorata and maculata are very transparent, the gut contents easily seen; the rest appear to be much less so. The larvae of verralli is smaller and darker than the rest. Final distinctions will have to be made on details of the head capsule, etc. The larvae marked * do not appear to have been described previously. 62 [April lateral II. veaTral 12. lateral L lirwola.. 1958] 63 Larval Descriptions Limnophila ( Limnophila ) punctata (Schr.) (figs. I, 2, 3, 4) The larvae measure about 22 mm. in length and 2 mm. in width when full grown. They vary from yellowish to dark brown, darker dorsally, with a small area to each side of the segmental constrictions lighter, giving a somewhat banded appearance. Pubescence thick and silky. Spiracular disc light in colour, with two small variable marks. Dorsal lobe small, lightly pigmented. Lateral and ventral lobes subequal, lightly pigmented over surface, darkened along distal part of border, and particularly at apex. The pigment of the lateral lobes extends to the outer border of the spiracles. Marginal hairs long and yellow on both disc and lobes, being about equal in length to the length of the lobes. Four anal papillae, about twice as long as broad, broad at base tapering towards tip, white. Found in moderately damp soil along banks of rivers, marsh soil, etc. Downham, Lancs. (72 larvae), 2.1. 1955; Whitewell, Yorks., 17.4.1956, etc. Limnophila ( Pilaria ) nemoralis (Mg.) (figs. 5, 6, 7, 8) The larvae measure about 16 mm. in length and 1.5 mm. in width when full grown, and are yellowish, slightly darker dorsally. Pubescence fairly thick, silky. Spiracular disc light in colour. Dorsal lobe small, lightly pigmented along a border inwards from actual margin. Lateral and ventral lobes subequal, with heavily sclerotized borders some distance in from margin. Marginal hairs short and whitish, not longer than half width of lobes at base. Four anal papillae, small, ovoid, white. Found in moderately damp soil by river banks, Whitewell, Yorks., I3-5-I957> Whalley, Lancs., 21.5.1956, etc. 64 4 Limnophila (. Fhylidorea ) lineola (Mg.) (figs. 9, 10, [April ii, 12) The larvae measure about 20 mm. in length by 2 mm. in width when full grown; usually yellowish, darker dorsally. Pubescence thick, almost iridescent. Spiracular disc light in colour. Dorsal lobe absent. Lateral lobes short with median heavily pigmented stripe extending to spiracles and forming a curve round the outside border. Ventral lobes longer with heavily pigmented median stripe extending on to spiracular disc. Marginal hairs on lobes long, and yellowish, longer towards the apex of each lobe; those on the ventral lobe much longer than those on the lateral lobes. Smaller hairs forming a line on the outside of each lobe leading to the fan of hairs round the lobe margin. A small bunch of darker hairs on lateral surface of anal segment. A line of darker hairs across ventral surface of segment immediately anterior to the anal papillae. Four anal papillae, ovoid, white. Found in marshy soil, soil of river banks, mud of cattle ponds, etc. Barley, Pendle, Lancs., 8.3.1956; Nelson, Lancs., 25.4.1957; Whalley, Lancs., 15.7.1957, etc. Limnophila ( Elaeophila ) verralli (Bergr.) (figs. 13, 14, 15) The larvae measure about 12 mm. in length and 1.25 mm. in width when full grown. They are whitish in colour, covered with fine pubescence. The anal segment is characteristic of this subgenus. The dorsal lobe is absent. Lateral and ventral lobes elongated into bluntly pointed processes, the ventral lobes slightly longer. All lobes have a rather sparse covering of dark, almost blackish hair, with some stronger bristles. According to Crisp and Lloyd (1954) this structure allows a bubble of air to be enclosed when the larva burrows. The lobes can be spread out when the surface is reached. Spiracles small. Four anal papillae, ovoid, white. Found in soil of river banks, especially sandy margins. River Hodder, White well, Yorks., 30.4.1955 (60 larvae); Downham, Lancs., 1.6.1956, etc. 1958] Limnophila (. Pseudolimnophila ) lucorum (Mg.) (figs. 1 6, 17, 18, 19) 65 The larvae measure about 18 mm. in length and 1.5 mm. in width when full grown. They are whitish with sparse pubescence, but darkened towards the anal segment where there is an abundance of coarse blackish pubescence. The dorsal lobe is absent, and the lateral lobes are small, heavily pigmented on the posterior surface, this pigment being continued across the spiracular disc underneath the spiracles to join with the pigment from the long ventral lobes. These latter are also heavily pigmented, and parallel sided. The marginal hairs are long and coarse, and so close set as to obscure details of the disc. On the ventral lobes the hairs are yellowish and almost as long as the lobe, becoming very slightly shorter towards the base of the lobes. Towards the base the hairs become whitish and the hairs of the lateral lobes and margin of the disc are also whitish but the bases of the hairs often appear darker. The whole spiracular disc is extremely shaggy. A line of very long blackish hairs forms a line across the ventral surface of the anal segment immediately anterior to the anal papillae. The anal segment apart from the disc is covered with short, blackish, coarse hair. L- verrqUI (.B>e.r