Dicrotendipes (Chironomidae, Chironominae, Chironomini) of Michigan - Identification

Adult Males
(modified from Epler 1987)

In addition to the generic description, the species in the key below have the following traits: Inferior volsella with simple apex, at most notched, appearing shallowly bifid or trifid, without a membranous dorsal extension; anal point not sharply reflexed ventrad, visible in dorsal view.

Pupae (modifed from Epler 1987)
Dicrotendipes botaurus Townes not keyed

1a a. Ventral spine row(s) absent 2
1b a. Ventral spine row(s) present on S II 4
 
2a(1a) a. 5 lateral lamellar setae on tergite VIII Dicrotendipes leucoscelis (Townes)
also: Anal lobe without dorsal shagreen; intersegmental spines present between tergites V and VI
2b a. 4 lateral lamellar setae on tergite VIII 3
 
3a(2a) a. Shagreen spinules on tergites II-V largest posteriorly, tips often rounded Dicrotendipes fumidus (Johannsen)
b. Exuviae light yellow-brown to dark yellow-brown
3b a. Shagreen spinules on tergites II-V more or less equal; Dicrotendipes nervosus (Staeger), Dicrotendipes lucifer (Johannsen) (nervosus-group)
b. Exuviae clear or light to dark brown
also: Medial shagreen spinules on tergite VI with longest spinules in middle of area; Exuviae clear with yellowish borders
 
4a(1b) a. 5 lateral lamellar setae on tergite VIII Dicrotendipes lobiger (Kieffer)
4b a. 4 lateral lamellar setae on tergite VIII 5
 
5a(4b) a. Caudolateral spur on tergite VIII double or triple, spurs well separated 6
5b a. Caudolateral spur on tergite VIII single or closely appressed double 7
 
6a(5a) a. Cephalic tubercles long, thin, sharply acute Dicrotendipes milleri(Townes)
b. 33-40 (mean 37) anal fin setae
6b Cephalic tubercles shorter, wider Dicrotendipes tritomus (Kieffer)
33-55 (mean 45) anal fin setae
 
7a(5b) a. Posterior spinules of median shagreen area on tergite VI larger, more rounded or longer than those of the anterior poirtion of the shagreen area Dicrotendipes tritomus (Kieffer)
b. Caudolateral spur on tergite VIII not strongly sinuate or recurved, almost straight
7b a. Posterior and anterior spinules of median shagreen area on tergite VI more strongly developed than those of the center 8
b. Caudolateral spur on tergite VIII usually strongly sinuate or recurved
 
8a(7b) a. Anal lobe with 31-50 (mean 38) lateral setae Dicrotendipes neomodestus (Malloch)
8b a. Anal lobe with 30-64 (mean 50) lateral setae Dicrotendipes modestus (Say)
 

Larvae (modifed from Epler 1987)
D. botaurus Townes and D. milleri Townes not keyed

1a a. Frontal apotome with a large anteromesal oval or subquadrate area 2
b. Frontal pit or process absent
1b a. Frontal apotome without such an area 3
b. A small anteromedian frontal pit or frontal process usually present
 
2a(1a) A frontoclypeal apotome present Dicrotendipes lobiger (Kieffer)
Sixth lateral tooth of mentum well-developed
also: Ventromental plate with 30-41 (mean 35) strial ridges
2b A fronto apotome present Dicrotendipes leucoscelis (Townes)
Sixth lateral tooth of mentum reduced or closely appressed to 5th
also: Ventromental plate with 37-60 (mean 52) strial ridges
 
3a(1b) a. Mentum with second lateral tooth almost completely fused with, or closely appressed to, the 1st, so that the 1st lateral tooth appears notched 4
3b a. Mentum with second lateral tooth at most only partially fusted to 1st lateral at base, 1st lateral tooth not appearing notched 5
 
4a(3a) a. Head capsule integument appears coarsely granular at 400x Dicrotendipes fumidus (Johannsen)
also: Postmentum or posterior portion of head capsule usually not darkened, rather yellow-brown to yellow-red-brown; 1st lateral teeth of mentum often turned outward
 
 
4b a. Head capsule integument at most appears slightly granular at 400x Dicrotendipes neomodestus (Malloch)
also: Anal tubules not reduced; at least the anterior outer margin of the ventromental plate usually crenulated
 
 
 
5a(3b) a. Proximal tooth of mandible saddle-shaped or with 2 points Dicrotendipes lucifer (Johannsen)
also: Sixth lateral tooth of mentum pointed
5b a. Proximal tooth of mandible mostly triangular in outline, not as above 6
 
6a(5b) a. Sixth lateral tooth of mentum rounded and closely appressed or fused to fifth lateral tooth Dicrotendipes nervosus (Staeger)
6b a. Sixth lateral tooth pointed, separate 7
 
7a(6b) Head capsule pale light brown to brown Dicrotendipes modestus (Say)
also: Anterior margin of ventromental plates with shallow to moderate crenulations
7b Head capsule pale yellow 8
 
8a(7b) a. Ventromental strial ridges 28-36 (mean 32) Dicrotendipes modestus (Say)
b. Postmentum usually darkened
8b a. Ventromental strial ridges 23-29 (mean 25) Dicrotendipes tritomus (Kieffer)
b. Postmentum rarely darkened
 

 

 

 


Page created: September 24, 2003; Last edited: November 8, 2013 (EB)