KEY TO THE PLECOPTERAN NYMPHS OF SOUTHWESTERN PENNSYLVANIA

 

 

1a. Thoracic gills present and highly branched, anal gills present or absent;…..........Perlidae; Acroneuria..6

1b. Gills found in coxal or cervical areas, unbranched and fingerlike or absent;........….....................................2

 

2a. Tips of glossa extend nearly to tips of paraglossae (Figure 2);.......................................................................3

2b.  Tips of glossa ending behing  paraglossae tips (Figure 3);.............4

 

  

 

Figure 2 Figure 3

 

3a. Tarsal segments 1 & 2 about equal in length; with conspicuous ventroapical triangular plate or with single gill located on coxae;.....................…..........…………................…........Taenioptergidae;Taeniopteryx.....8

3b. Tarsal segment 2 distinctly shorter than tarsal segments 1 and 3;...….......................……............................5

4a. The basal diameter of the maxillary palp terminal segment is about equal to the diameter of the penultimate segment (Figure 4); the wingpads of the metathorax are strongly divergent from the long body axis; the cerci are longer than or equal to the length of the abdomen;................…..Perlodidae; Isoperla......10

4b. The basal diameter of the maxillary palp terminal segment is distinctly smaller than the diameter of penultimate segment (Figure 5); the wingpads of the metathorax are slightly divergent from or parallel to the long body axisl; cerci length is less than the length of abdomen;...............................Chloroperlidae....12

  Figure 4 Figure 5

 5a. One up to six abdominal segments divided by a membranous fold; anal lobe of metathoracic wingpad is small and does not extend beyond center of wingpad (Figure 6);.........….……..Lecturidae; Leuctra tenius

5b. One to nine abdominal segments divided by a memgranous fold; anal lobe of metathoracic wingpad extends beyond the center of wingpad (Figure 7);……….....................................................…...Capniidae.......13

 

Figure 6 Figure 7

 

6a. Acroneuria: Gills in anal region present;.........................................................................................……............7

6b. Gills in anal region absent;.........................................................................................................….A. abnormis

 

7a. Conspicuous transverse dark band on the posterior edges of tergites is present; a pale but distintict ‘W’ shape is present anterior to the ocelli;........................................................................…………....A. lycorias

7b. Lacking dark transverse bands on rear edges of tergites; from posterior edge of head, a pale line extends between the rear ocelli and continues into the triangle formed by the ocelli;.......................A. evoluta

8a. Taeniopteryx: All setae of tergites are long and curled; a stripe extends on to the head and is wide on the occiput;....................…………………...............…….............................................................................T. metequi

8b. Setae of the posterior edge of tergites is short and blunt, others are long and curled; a narrow stripe extends on the occiput region of the head;...................…………….....…...............................................................9

 

9a. Hind femur with a tooth or spur at middle of inner margins (of mature males);..…..........…........T. maura

9b. Hind femur without distinct tooth or spur at middle of inner margin (may see thickening)……...T. burski

 

10a. Isoperla: Abdominal dorsal surface is with dark longitudinal banding (Figure 8); the clypeus contains a dark colored square; on the head is a transverse band encircling two white spots on each side of the anterior ocellus;...........................…………………….................................................................................I. bilineata

10b. Abdominal dorsal surface is without distinct longitudinal banding (Figure 9),is spotted, uniform or banded transversely;……………...............................................................................................................................11

Figure 8 Figure 9

 

11a. A dark transverse line on head extends between compound eyes and connects the rear ocelli;.,,..I. clio

11b. The posterior edges of tergites have black conspicuous bands; clypeus is dark colored;…....I. signata

 

12a. At head’s hind edge and between the compound eyes there are less than six course setae; the dorsal surface of the pronotum contains few and fine setae;……………......................................................Haploperla

12b. Between the compound eyes at the head’s hind edge there are more than six course setae; the dorsal surface of the pronotum contains course setae;..……………....................................................Sweltsa mediana

 

13a. Many obvious abdominal setae present; wingpads are rounded;................…….......................Paracapnia

13b. No abdominal setae; truncate wingpads with a notch near the tip;............…….........................Allocapnia

 

14a. Paracapnia: Tibial setae of inner surface short (length equals 1/2 tibial width;...........……...P.angulata

14b. Tibial setae of inner surface long (length equals tibial width);....................................……..............P. opis

 

15a. Allocapnia: Tergites have terminal and intermediate rows of straight standing setae (Figure 10);.......16

15b. Abdominal tergites have terminal row of straight standing setae only (Figure 11);.......................A. recta

Figure 10 Figure 11

 

16a. Long straight standing setae on the tergite margin; few intermediate setae present;..........…...A. rickeri

16b. Short straight standing setae on the tergite margin; many intermediate setae present;................…....17

 

 17a. When viewed from the side, the pronotum and head contain numerous setae; specimen may be without wing pads;..........................................................................................………………………......A. vivipara

17b. When viewed from the side, the pronotum and head do not contain many setae; the wingpads are truncated;.......................……………………............................................................................................A. granulata

 

 

 

SOURCES

 

 Peckarsky, B.L., Fraissinet, P. R., Denton, M.A., and Conklin, D.J. (1993). Freshwater

Macroinvertebrates of Northeast North America. Comstock Publishing Associates, Ithaca.

 Surdick, R.F. and Kim, K.C. (1976). Stoneflies (Plecoptera) of Pennsylavania: A Synopsis.

Pennsylvania State University, University Park.

 Usinger, R.L. Editor. (1963). Aquatic Insects of California. 2nd Ed. Regents of the University of

California, Berkeley.

 

Links:

Plecoptera of Pennsylvania