Sialidae - Alderflies
Adults
1a Apex of abdomen without an ovipositor, but with a more or less complicated
assemblage of parts - 2, males
1b Apex of abdomen with a broad, rounded ovipositor - 11, females
2a(1a) Sternite of Ab9 produced into a flap covering most of the genitalia;
also: apex of lateral plates without a tooth; terminal plate narrowed at apex
and not markedly incised - Sialis vagans Ross
2b Sternite of Ab9 not produced into a flap - 3
3a(2b) Terminal plate produced at apex into a pair of long arms - 4
3b Terminal plate sometimes with an apical incision, or a pair of short "horns," but
not with a pair of long arms - 5
4a(3a) Apical arms of terminal plate separated at their base by a distance
almost equal to their length - Sialis hasta Ross
4b Apical arms of terminal plate close together at base, and converging at
tip - Sialis mohri Ross
5a(3b) Legs with femora rufous and tibiae the same color or blackish - 6
5b Legs black, or with tibiae slightly lighter than femora - 7
6a(5a) Head smooth and polished - Sialis glabella
6b Head punctured and dull - Sialis americana (Rambur)
7a(5b) Genital hooks long and whiplike, extending forward between the lateral
plates - 8
7b. Genital hooks short, never longer than the plate from which they arise;
lateral plates always closely appressed on meson; also: Apex of terminal plate
not with hornlike or necklike processes; basal portion of of genital plates
neither enlarged nor projecting over the terminal plate; Ab9 sternite with
lateral setae fairly short
10
8a(7a) Apex of lateral plates produced into large knobs - Sialis infumata Newman
8b Apex of lateral plates not knoblike; also: Terminal plate short, its apex
markedly cleft; genital hooks with a basal lobe - 9
9a(8b) Basal lobe of genital
hooks relatively short, somewhat triangular, about <1.5x long as greatest
width, as in figure (reversed in Ross 1937?) - Sialis velata Ross
9b Basal lobe of genital hooks long, markedly robust compared with distal
lobe, basal end of lobe somewhat rectangulate, about 2x long as greatest width,
as in figure - Sialis itasca Ross
10a(7b) Terminal plate with the apex narrow, tapered to a blunt point and
not incised on meson - Sialis iola Ross
10b Terminal plate with apex wider, almost truncate; also: Terminal plate almost
as wide as long, more or less pentagonal; genetial plates > 1/3 as long
as terminal plate - Sialis joppa Ross
11a(2b) Sternite of Ab9 large, triangular and distinctly sclerotized - Sialis
mohri Ross
11b Sternite of Ab9 apparently membranous and difficult to distinguish in uncleared
specimens - 12
12a(11b) Legs with femora rufous and tibiae the same color or darker than
femora - 13
12b Legs either entirely black or with the tibiae lighter than the femora -
14
13a(12a) Head smooth and polished - Sialis glabella
13b Head punctured and dull - Sialis americana (Rambur)
14a(12b) Ab8 sternite narrow and divided into two separate lobes by a median
desion - Sialis aequalis Banks, Sialis vagans Ross
14b Ab8 sternite either wider, or not divided so completely into two separate
parts - 15
15a(14b) Ab8 sternite as in figure, rectangular and with the distal portions
set out as distinct swellings - Sialis infumata Newman
15b Ab8 sternite not as above, either with apex rounded out, or not set off
with such conspicuous lobes - 16
16a(15b) Ab8 sternite flat, not tilted so that the apical margin is raised;
bursa copulatrix with a terminal fingerlike process - Sialis velata Ross, Sialis
itasca Ross
16b Ab8 sternite tilted so that the apical margin is markedly raised and the
basal margin depressed; bursa copulatrix with terminus triangular - Sialis
iola Ross, Sialis joppa Ross
Sialis aequalis Banks, 1920
mSialis americana (Rambur, 1842), Semblis
Sialis driesbachi Flint, 1964
mSialis hasta Ross, 1937
mSialis infumata Newman, 1838
mSialis itasca Ross, 1937
mSialis joppa Ross, 1937
mSialis mohri Ross, 1937
mSialis vagans Ross, 1937
mSialis velata Ross, 1937
Larvae (after Canterbury 1978)
1a Venter of abdomen with distinct crossbands, or solidly
dark with pigment - 2
1b Venter of abdomen light in color, and lacking distinct
cross bands, or with incomplete bands - 5
2a(1a) Background color of head and thorax dark with distinct
lighter markings on head and pronotum - 3
2b Background color of head and thorax with faint markings on head
and pronotum - 4
3a(2a) Labrum with a snout-like front; venter of abdomen
with all but the last segment darkened completely, a narrow white line along
the lateral edges - Sialis iola
3b Labrum without snout-like front as
above; venter of abdomen with incomplete dark bands at edge of each segment
- Sialis hasta
4a(2b) Pronotum with only a posterior pronotal medial
spot visible, lateral elliptical spots large and ovoid on a dark background;
labral
marginal setae, usually 12 per side; meso- and metanotal patters as illustrated
- Sialis joppa
4b Pronotum
with pronotal medial spots faint; labral marginal setae usually 15 per
side; meso- and metanotal patters as illustrated, with parts thickened
and joined - Sialis aequalis
5a(1b) Mandible with a third tooth present; markings
on head and thorax dark on a light background - Sialis glabella
5b Mandible without a distinct third tooth,
represented only by a slight protuberance; head and thoracic figures light
on a darker background - 6
6a(5b) Dorsum of abdomen with markings forming an anchor-like figure on
each segment; pronotum with a rectangular light area at its center - Sialis
vagans
6b Dorsum of abdomen with usual chevron markings; pronotum not as above -
7
7a(6b) Pronotum with small, dark elliptical pronotal spots, median portion
light; venter of abdomen with cross bands incomplete at midline or absent
- Sialis infumata Newman
7b Pronotum without dark elliptical pronotal spots, pattern may be indistinct;
venter of abdomen usually white -
8
8a(7b) Head with darkened markings; pronotal medial spots dark; mesonotum
and metanotum as in figure - Sialis itasca Ross
8b Head patterns faint; pronotal medial spots barely visible if at all; mesonotum
and metanotum not as above - 9
9a(8b) Mesonotal figures with parts thickened and fused at median suture
- Sialis velata Ross
9b Mesonotal figures with parts slim and not fused as above - Sialis
mohri Ross