Heterotrissocladius brundini spec. nov. from Norway 
(Diptera, Chironomidae) 
By Ole A. Ssether and 0yvind A. Schnell 
Abstract 
Heterotrissocladius brundini spec. nov. is described in all stages and both sexes. It apparently form the plesiomor- 
phic sister species oi H. maeaeri Brundin. 
Introduction 
Langton (1984: 88, fig. 28 a) illustrated a pupa oi Heterotrissocladius with imbedded spines on Seg- 
ments VI -VIII and very large frontal warts. During an investigation of some acidified lakes in the sou- 
thernmost part of Norway the junior author found all stages of apparently the same species. Later it 
was found also in western and northwestern Norway. 
Methods and morphology 
Morphological nomenclature follows SitTHER (1980) with the exception that the apical spine of the gonostylus 
is termed the megaseta. The measurements are given as ranges followed by a mean when four or more measurements 
are made, followed by the number measured in parentheses (n). 
The type material is kept at the Museum of Zoology, University of Bergen (ZMB). 
Heterotrissocladius Spärck 1922, emended 
Imago — Eyes completely naked, with a few microtrichia between marginal ommatids or pubes- 
cent, i. e. with microtrichia between all ommatids, with reticulation between central ommatids. 
Otherwise as in Sii;THER (1975: 3). 
Pupa — Frontal warts weak to strongly developed. Frontal setae on frontal apotome (most species) 
or onprefrons (atleast/f. latilaminus Sxther). Caudolateralcornersof segments Vl-VIIIoccasionally 
with inner sclerotization resembling imbedded spines (H. brundini spec. nov), these strong on VII, 
weaker on VI, and only indicated on VIII. Otherwise as in Sxther (1975: 4). 
Larva — Anterior parapods with apical claws grading over into basal hair-Hke spines anteriorly and 
on a common base. Otherwise as in Sxther (1975: 4). 
57 
Heterotrissodadius brundini spec. nov. 
(Figsl-3) 
Heterotrissodadius Pe 1, Langton 1984: 88 
Type locality: Norway, Aust-Agder, Birkenes, Lake Repstadvatn. 
Type material: Holotype, male, Lake Repstadvatn, Birkenes, Aust-Agder, Norway, 19/9/86, leg. H. Sa:grov & 
0. A. Schnell, in coli. Mus. Zool. Univ. of Bergen (ZMB No. 1 1 5). 
Paratypes: 5 males, 4 females, 2 male pupae, 147 pupal exuviae, 6 larval exuviae, as holotype; 5 pupal exuviae, 
Lake Store Hovvatn, Birkenes, Aust-Agder, Norway, 6/9/86, 0. A. Schnell mature female pupa, Lake Jolster, Jol- 
ster, Sogn & Fjordane, Norway, 18/8/87, H. Ssgrov; mature male pupa, Lake Litlebovatn, Volda, More & Roms- 
dal, Norway 26/7/86, 0. A. Schnell; Other material (?): Male, Nordseter, Lillehammer, Oppland, Norway, 31/8/ 
86, R. Bergo. 
Diagnostic characters 
The normal clypeus and cibarial pump combined with the moderately short acrostichals starting 
some distance from the scutal projection and the few setae on the wing membrane will separate the 
species from other Heterotrissodadius except H. maeaeri Brundin. However, the stipes is reduced, the 
wing slightly darker, the AR lower (0.7-1.1), the LRj higher (0.76-0.78) and the number of setae in 
cell r4+5 usually lower (7—18, except in one mature male pupa apparently with about 50 setae and an- 
other possible specimen with 45 setae, see remarks) in H. brundini spec. nov. The pupa can be separat- 
ed from other members of the genus by means of the large frontal warts and the imbedded spines on 
Segments VI-VIII. The larva can be distinguished by the narrowly separated two median teeth of the 
mentum with distinct lateral notches, the brownish black submentum which is conspicously darker 
than the surrounding areas of the head capsule, and the VM ratio of 1.1 — 1.5. 
Etymology : Named in honour of Prof. emer. Lars Z. Brundin to his 80 year birthday and to signify his eminent 
contribution to chironomidology and lake typology where Heterotrissodadius has occupied a central position. 
Description 
Male imago (n = 7—9, except when otherwise stated). 
Total length 3.93-4.22, 4.03 mm (6). Wing length 2.10-2.19, 2.14 mm (4). Total length/wing 
length 1.82-1.96, 1.90 (4). Wing length/length of profemur 2.44-2.55, 2.50 (4). Coloration brown 
with central parts of scutellum conspicuously pale. Wing pale yellowish brown. 
Head. Eye with weak microtrichia between all ommatids. AR 0.92 — 1.05, 0.98 with one antennaof 
one specimen with an AR of 0.68. Ultimate flagellomere 424—484. 460 fxm long with one antenna of 
one specimen with ultimate flagellomere 381 /u.m long. Pedicel 129—160, 139 /ttm wide. Temporal 
setae 10 — 17, 14, including 3 — 5, 4 inner verticals; 2 — 5, 4 outer verticals; and 5 — 8, 7 postorbitals. 
Clypeus 123 — 138, 132 /um wide; with 6—13, 10 setae. Cibarial pump, tentorium and stipes as in 
Fig. 1 A, of doubtful specimen from Nordseter as in Fig. IB. Tentorium 150—176, 162 /xm long, 
35 — 55, 42 /u,m wide. Stipes with reduced sclerotization in basal half and reduced median plate; 
105 — 139, 120 /u.m long; 19 — 38, 26 /u,m wide (normal in possible specimen from Nordseter, see re- 
marks). Palp lengths (micrometers): 29-45, 32; 41 -62, 51; 109-149, 134; 86-103,98; 106-138, 125. 
Third palpal segment with 2 — 4, 3(6) sensilla clavata at apex. 
Thorax (Fig. 1 C). Antepronotum with 6— 14, 1 1 setae. Dorsocentrals 15 — 25, 18; acrostichals 5 — 9, 
7, starting some distance from scutal projection ranging from '/3— '/2 the length of scutum, longest 
acrostichal 38 — 56, 45 /ttm long; prealars 7—9,8. Scutellum with 16—23, 19 setae. 
Wing (Fig. ID). VR 1.13-1.19, 1.16 (4). Brachiolum with 1-2, 2 setae; R with 11-15, 13 (6): Ri 
with 4- 1 1, 7 (6); R4+3 with 7-10, 9 (6); M,+2 with 0-8, 2 setae; other veins bare. Cell r4+5 with 7- 1 8, 
14 (5) setae, apparently with about 50 setae in mature male pupa from Volda; cell m,+2 with — 3, 
1 seta; cell an with 0—1, setae. Squama with 18—21, 19 setae. 
58 
Legs. Spurof fronttibia47— 56, 50 /xm long; spursofmiddle tibia 35 — 38,36 )U,mand21— 34, 25 fxm 
long; of hind tibia 50 — 67, 62 jU,m and 18—26, 22 fim long. 
Width at apex of front tibia 44-50, 47 ^tm (4); of middle tibia 47-53, 49 fim (4); of hind tibia 
56—59, 56 ^im (4). Comb with 11 — 12, 11 setae; shortest seta21— 29, 24 />tm long; longest seta53 — 70, 
61 ^tm long. Sensilla chaetica absent. Lengths (micrometers) and proportions of legs (n = 4): 
Fig. 1. Heterotrissocladius spp, ma.\e[m2igo: A, C — E. H. brundinispec.nov;B,F.H. brundini ormaeaeri (Bvun- 
din); A, B. Cibarial pump, tentorium and stipes; C. Thorax; D. Wing; E — F. Hypopygium. 
Hypopygium (Fig. IE). Anal point 53 — 70, 63 /xm long; tergite IX including anal point with 
20-27, 23 setae; laterosternite IX with 4-8, 7 setae. Phallapodeme 117-139, 125 fjum long; transversa 
sternapodeme 106 — 116, 111 [xm (6) long. Virga very weak and inconspicuous, consisting of one or 
59 
two Clusters of all together 6 — 7 spines; 11 — 15, 13 fjnn (5) long. Gonocoxite 255 — 278, 268 /xm long; 
inferior volsella rounded, with long setae on distal side. Gonostylus 117—141, 127 /u,m long; outer 
margin rounded; crista dorsalis long, relatively pronounced, rounded near apex; megaseta 10—15, 
12 fjim long. HR 1.96-2.28, 2.12; HV 2.95-3.46, 3.18. 
Female imago (n = 9—11, except where otherwise stated). 
Total length 3.28-4.00, 3.61 mm. Wing length 2.11-2.33, 2.18 mm. Total length/wing length 
1.51-1.80, 1.66. Winglength/lengthofprofemur 3.01-3.24, 3.12 (8). Coloration as in male. 
Head. Flagellomere lengths (micrometers): 83-109, 98; 45-60, 55; 53-64, 59; 56-69, 64; 
120-156, 136. Pedicel 68-82, 73 /itm wide. AR 0.44-0.55, 0.50. Temporals 9-14, 12; including4-6, 
5 inner verticals; 2 — 5, 3 outer verticals; and 2 — 5, 3 postorbitals. Clypeus 138 — 161, 151 fim wide; 
1.85 — 2.22, 2.06 times as wide as pedicel; with 7—15, 11 setae. Tentorium 138 — 154, 146 /xm (8) long; 
18-26, 22 fim (8) wide. Stipes 86-149, 1 18 /xm (8) long; 9-23, 16 /xm (8) wide. Palp segments length 
(micrometers): 26-35, 31; 38-49, 43; 82-103, 94; 68-88, 78 (7); 98-135, 118 (7). Two specimens 
with fourth and fifth palp segments fused; 120—135 /tm long. Third palpal segment with 3 — 5, 4 sen- 
silla clavata at apex. Coronal suture incomplete; 64 — 98, 82 fxm long. 
Thorax. Antepronotum with 8—17, 11 lateral setae. Dorsocentrals 14 — 29, 19; acrostichals 4 — 7, 5; 
prealars 6—10, 8. Scutellum with 16 — 24, 19 setae. 
Wing.VRl.11-1.16, 1.13. Brachiolum with 2 setae; R with 12-25, 17; R, with 5- 13,8; R4+5 with 
12 — 33, 24; M1+2 with 0—2, 1 setae; other veins bare. Cell r4+5 with 23 — 54, 36; cell mi+2 with 4—17, 
13 (8) setae; cell an with 2— 14, 6 (8) setae. Squama with 15—25, 21 setae. 
Legs. Spur on front tibia 41—56, 50 /im long; spurs on middle tibia 30—41, 37 /xm and 23 — 34, 
28 /xm long; on hind tibia 60 — 71, 66 /xm and 18—26,24 /xm long. Width at apex of front tibia 38 — 47, 
43 /xm; of middle tibia 41—53, 48 /xm; of hind tibia 49—59, 53 /xm. Comb of 7—10, 8 setae; shortest 
seta 23-34, 29 /xm long; longest seta 49-67, 56 /xm long. Sensilla chaetica 1 -7, 4 at 0.20-0.30, 0.28 
(8) to 0.40 — 0.60, 0.53 on ta, of hind leg; apparently absent in mid leg. Lengths (micrometers) andpro- 
portions of legs (n = 7 — 9): 
P, 669-753 753-8« 5A8-624 274-321 19A-217 137-151 99-131 0.72-0.76 2.68-2.92 2.47-2.63 2.1-3.1 
697 793 582 291 200 143 106 0.74 2.87 2.54 2.9 
P 690-807 717-807 359-384 191-227 142-167 95-120 85-114 0.49-0.51 3.23-3.47 3.76-4.10 2.1-3.0 
716 749 377 203 149 106 99 0.50 3.31 3.89 2.5 
P 784-896 884-992 548-624 293-335 227-263 135-161 99-134 0.61-0.65 2.78-2.98 2.88-3.10 2.9-3.9 
817 921 576 303 242 144 114 0.63 2.88 3.02 3.3 
Abdomen. Number of setae on tergites I-VIII as: 33-53, 42; 38-46, 42; 26-40, 25; 24-44, 34; 
24-38, 31; 19-35, 28; 19-35, 24;9-26, 16. Number of setae on sternites I-VIII as: 0; 3-7, 5; 5-10, 
7; 8-17, 11; 12-20, 15; 14-24, 17; 15-23, 18;43-71,56. 
Genitalia (Fig. 2). Gonocoxite with 13 — 20, 16 setae. Tergite IX well divided, with 20 — 31, 25 setae. 
Cercus 114—142, 133 /xm long. Seminal capsule 76—101, 86 /xm (8) long; excluding 11—26, 17/xm 
long neck; 64 — 79, 71 /xm wide. Notum 105 — 161, 132 /xm long. 
Pupa (n = 11, except when otherwise stated) 
Total length 3.76 — 4.78, 4.31 mm (9). Lengthof thoracic horn/lengthof anal macrosetae 1.10—1.50, 
1.34. Thorax of exuviae pale brownish grey, abdomen nearly transparent. 
Cephalothorax. Frontal warts (Fig. 3A) conspicuous, 82—117, 97 /xm high; 35 — 53, 40 /xm (10) 
wide at base. Frontal setae on frontal apotome; 59 — 83, 73 /xm (8) long. Postorbitals 59 — 73, 66 /xm (4) 
and 41-56 /xm (2) long. Median antepronotals 117-147, 140 /xm (9) and 103-132, 120 /xm long; la- 
teral antepronotals 73 — 88, 80 /xm and 0—44, 9 /xm long (when absent reduced to setal mark). Thoracic 
hörn (Fig. 3B) 290-396, 349 /xm long; 44-70, 54 /xm (9) wide; 5.44-8.00, 6.57 (9) times as long as 
wide. Anterior dorsocentral 44 — 88, 65 /xm long; Dcj 53 — 117, 88 /xm long; DC3 32 — 129, 68 /xm long; 
60 
Fig. 2. Heterotrissodadius brundini spec. nov, female genitalia: A. Dorsal view; B. Ventral view; C. Lateral view; 
D. Lobes of gonapophysis VIII (DmL dorsomesal lobe; VIL, ventrolateral lobe; ApL, apodeme lobe). 
Dc4 64 — 88, 78 ^im long. Distance between Dcj and Dc2 18 — 67, 42 /xm; between Dc2 and Dcj 15 — 53, 
28 ^im; between DC3 and DC4 23 — 82, 58 /xm. Prealar observed in one specimen, 18 fjbm. long. Wing 
sheath with fine marginal lines. 
Abdomen (Fig. 3 C, D). Shagreen absent on tergite I (T I) and T IX, weak median on T II, more ex- 
tensive and stronger posterior on Till— VI, weak anteriomedian on T VII— VIII. Sternites I (S I) and 
IX bare, S II — III with weak anterior and median shagreen, S IV— VIT with weak anterior shagreen and 
a few posterior spinules as S VI. Pedes spurii A present on sternites IV- VII and occasionally VIII (3 in- 
dividuals). Pedes spurii B wider than high. Caudal hooklets 20—40, 32 on T II. Sternite VIII of male 
with 19 — 33, 27 (7) posterior spines. Caudolateral corners of segments VI— VIII with imbedded spi- 
nes, distinct on VII, only indicated on VI and VIII. L setae on segments I— VIII as: 1—2 (4): 3:3:3: 
3: 3: 3 — 4, 3: 5; 3 lamelliform on VII, 4 lamelliform on VIII, occasionally also fifth L seta on VIII 
shghtly lamelliform. Anal lobe 269-337, 302 )U,m long; with 19-25, 22 setae in fringe; anal macrosetae 
234—293, 261 ^tm long. Genital sac of male overreaching anal lobe by 88-124, 109 /am (4). 
Larva (n = 6, except when otherwise stated) 
Total length about 6 mm (larval exuviae). Head capsule length 447—502 />tm (3). 
Head. Antenna as in Fig. 3E. Lengths of antennal segments (micrometers): 82 — 88, 86; 35 — 41, 36; 
3-4, 4; 18-22, 19 (4); 6-9, 7 (4); 4-6, 4 (4). AR 1.07-1.16, 1.12 (4). Basal antennal segment 18-21, 
20 jLim wide; 4.05—4.32, 4.24 times aslongaswide; distance from baseto annular organ9 — 18, 15 /xm; 
to distal mark of seta 21—35, 31 /xm; blade at apex 50—64, 50 /xm long; accessory blade 7—9, 9 /xm 
long. Subapical style of second segment 6-9, 7 /xm (5) long. Labrum and epipharyngeal areas as in 
61 
Fig. 3. Heterotrissodadius brundini spec. nov, pupa: A. Frontal apotome; B. Thoracic hörn; C. Tergites of male; 
D. Sternites of male. - larva: E. Antenna; F. Labrum and epipharyngeal area; G. Mandible; H. Maxilla; I. Mentum. 
62 
Fig. 3F. S I broad, finely plumose. Labral lamellae rounded apically. Median spine of pecten epipha- 
ryngis narrower than lateral spines. Premandible 79—85, 83 /x.m (5) long. Mandible (Fig. 3G) 
158 — 176, 168 fjim (4) long. Maxilla as in Fig. 3H. Mentum (Fig. 31) with two close median teeth each 
with distinct lateral accessory tooth, width of one median tooth including accessory tooth 18—21, 
19 /Lim; ventromental plates 21—26, 25 /xm (4) wide; 1.08 — 1.50, 1.32 times as wide as one median 
tooth including accessory tooth. Postmentum distinctly darker than surrounding areas of head cap- 
sule; 208-229, 222 /xm long. 
Abdomen. Procercus 38—47, 43 /xm high; 29—32, 31 fxm wide; anal setae 647—747, 706 /xm (5) 
long. Supraanal seta 234—264, 242 /im long; 0.32 — 0.35, 0.34 (5) times as long as anal setae. Anal tubu- 
les and posterior parapods not measurable. 
Remarks 
A male imago from Nordseter near Lillehammer is not included in the type material. Judging from 
the leg proportions and the antennal ratio the specimen belong to H. hrundini. The normally 
sclerotized stipes (132 /tm long, Fig. 1 B) and the more numerous setae on the wing membrane (45 
setae in cell r4+5, 7 setae in each of m^ +2 and m3+4), however, indicate that it belongs to H. maeaeri. The 
hypopygium (Fig. 1 F) could belong to any of the two species. Associated pupal material is needed to 
decide whether the stipes and the wing setation is more variable within H. hrundini or whether the 
specimen represents H. maeaeri or an additional new species. 
The pupa described by Langton (1984: 88) do not quite fit H. hrundini. The thoracic hörn oiHete- 
rotrissocladius Pe I of Langton is wider (length/width 4.0 — 5.1), and there are more numerous setae in 
the anal lobe fringe (26 — 30). These variations, however, probably is not more than can be expected 
between various populations. 
Ecology and distribution 
H. hrundini has been found in two acidified lakes in Southern Norway, two lakes in the provinces 
of More & Romsdal and Sogn & Fjordane, and in Lake Assynt in the Sutherland District of Scotland. 
It could conceivably be an indicator species of oligotrophic acid lakes. 
_ Systematics 
SyETHER(1975: 57— 62, fig. 15) does aphylogenetic analysis oi Heterotrissocladius and related genera. 
In the scheme of argumentation H. hrundini will be synapomorphous for trends 57, 58, 59, 60; 9, 10, 
11; and 51, 52, showing that the species is a good Heterotrissocladius. It is symplesiomorphous for 
trends 41 and 44, apomorphous for trends 42 (reduced acrostichals) and 43 (reduced number of setae 
on the wing membrane). The last two trends show parallelisms between the suhpilosus and the maeaeri 
groups. However, there are no pearl rows on the pupal wing sheaths (trend 37), only 4 filamentous se- 
tae on Segment VIII of the pupa (trend 39), and no setae dorsad of the genital sac (trend 40), showing 
that the species belong with the maeaeri and marcidus groups. However, the pedes spurii A which may 
occur on sternite VIII and the fifth L seta which in some specimen is somewhat filamentous, indicate 
a plesiomorphic position within these groups. 
The species is synapomorphous with H. maeaeri for trends 32 (short acrostichals) and 35 (distribu- 
tion of L setae in pupa). It is plesiomorphous for trends 33 (PSB), 34 (PSA), 36 (median teeth of men- 
tum), and apomorphous for trends 30 (setae on male tergite IX) and 31 (AR of larva), indicating a pla- 
cement in the marcidus group. However, trends 30 and 31 are not very significant, representing con- 
tinuous Variation and probably good only as specific autapomorphies. Also several additional synapo- 
morphies between H. maeaeri and H. hrundini can be found in the male hypopygium in the shape of 
the inferior volsella, the inner margin of the gonocoxite and in the shape of the gonostylus. We feel re- 
latively certain about the phylogenetic position of the species as the sister species of H. maeaeri. 
63 
There are few problems fitting the imagines and the pupa within the concept of the maeaeri group 
(S/ETHER 1975: 22); the stipes of the imagines and the pedes spurii B of the pupa have to be deleted 
as distinguishing characters. However, the larva will key to H. marcidus (Walker) in the larval key 
(S.€THER 1975: 9) because of the two median teeth of the mentum. The median teeth, however, are 
closer together than in other described species except for Heterotrissodadius sp. E from Lake Superior 
(Si^THER 1975: 55) which is mentioned as intermediate between the marcidus and maeaeri groups. 
Heterotrissodadius sp E almost certainly is close to H. brundini. A redefinition of the maeaeri group 
to include larvae with median teeth close together and distinct accessory teeth will make a Separation 
between the maeaeri and marddus groups still feasible. 
The imbedded spines found in the pupa is nearly unique within the orthoclads, otherwise found in 
some members of Zalutschia Lipina only. S^ther (1976) did not attempt to classify Oliveridia Ssether, 
Hydrobaenus Fries, Trissodadius Kieffer and Zalutschia combined as a monophyletic group. Accor- 
ding to S^THER (1977: 82), however, the genera apparently form a monophyletic unit based on the 
shape of the female gonapophysis VIII. This trend, however, is rather insecure as similar gonapophy- 
ses occur elsewhere including in the Heterotrissodadius group of genera. It thus is possible that Zalut- 
schia is more closely related to the Heterotrissodadius group than to Hydrobaenus, and that the im- 
bedded spines represent an underlying synapomorphy occurring in some, bot not all members of both 
Zalutschia and Heterotrissodadius. We have observed indication of imbedded spines also in some ex- 
uviae of //. marcidus. On the other band the imbedded spines merely represent a strengthening of the 
paratergital margin and could easily be a result of parallel selection. 
The larvae of Heterotrissodadius all have hair-like spines at base of the anterior parapods similar to 
those illustrated by Strenzke (1950 fig. 1 1) for Paraphaenodadius Thienemann, but not found in Pa- 
rametriocnemus Goetghebuer or apparently in the same form in other orthoclads. However, other 
synapomorphies seem to confirm the relationship shown by S^ther (1975 fig. 15) and these spines 
must be regarded either as secondarily reduced in Parametriocnemus or as an underlying synapomor- 
phy for the whole group. 
Acknowledgements 
We would like to thank Laboratory for Freshwater Ecology and Inland Fisheries Bergen for financial support. 
We also are indebted to Mr. Tien van Trieu for doing the illustrations and to Mrs. N. Waagsberg for typing the ma- 
nuscript. 
Literature 
Langton, P. H. 1984: Akeytopupalexuviaeof British Chironomidae. - P. H. Langton, March, Cambridgeshire, 
324 pp 
S^THER, O. A. 1975: Nearctic and Palaearctic Heterotrissodadius (Diptera: Chironomidae). - Bull. Fish. Res. Bd 
Can. 193: 1-67 
1976: Revision oi Hydrobaenus, Trissodadius, Zalutschia, Paratrissocladius, and some related genera (Diptera: 
Chironomidae). - Bull. Fish. Res. Bd Can. 195: 1-287 
1977: Female genitalia in Chironomidae and other Nematocera:morphology,phy logenies, keys. — Bull. Fish. 
Res. Bd Can. 197: 1-209 
1980: A glossary of chironomid morphology terminology (Chironomidae: Diptera). — Ent. scand. Suppl. 15: 
1-51 
Strenzke, K. 1950: Systematik, Morphologie und Ökologie der terrestrichen Chironomiden. — Arch. Hydrobiol. 
Suppl. 18(2): 207-414 
Prof. Ole A. Sa;ther 
0yvind Schnell 
Museum of Zoology 
University of Bergen 
N-5007 Bergen, Norway 
64