Aeshnidae Selys -Darners

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Page last updated: 25 June1998

Notes on Michigan Aeshnidae

Aeshnid larvae are conspicuous, bare-skinned,thin-legged larvae that are widespread in freshwater, found clingingupon aquatic vegetation, stems and other trashy material along andnear the waters' edge. Their laterally positioned, well-developedeyes are amongst the largest of all odonates, and are well suited totheir clinging habits and aggressive predatory techniques (seeCorbet1962).

These larvae are easily distinguished fromother anisopteran larvae by the long, flat mentum, a prementum thatis at most slightly cleft (usually not), antennae with at least 6 to7 segments, and generally smooth abdomen that (except forNasiaeschna) have no mid-dorsal prominences or hooks. Except fortwo genera not found in Michigan, the labial palps are withoutraptorial setae. The abdomen is widest in the middle segments, andappears somewhat triangular or hemispherical in cross-section. Likethat of Zygoptera, eggs of adults are laid endophytically (in planttissue), and the developing genitalia of maturing female larvae areoften helpful species-level diagnostic characters. Some aeshnids havedirect development, others have significant periods of egg diapause(see Walker1958, Corbet 1962).

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Generic Key to Mature Larvae of MichiganAeshnidae
(Adapted from
Westfall andTennessen 1996)

1a. Hind angles of headdecidedly angulate (picture); Ab5-9 with well-developed lateralspines (picture) - 2

1b. Hindangles of head rounded (picture); Ab6-9 or 7-9 with well-developedlateral spines (picture); Aeshnaeremita, which has hind angles of headbluntly angular (picture), has minute lateral spines on abdominalsegment 5 (picture) - 5

2a.(1a). Abdomen broadly rounded (picture) -3

2b. Abdomenwith distinct middorsal ridge (picture) - 4

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3a.(2a). Distal margin of palpal lobes truncate (picture);often with evident pale, dorsal spot on abdominal segment 8, andparaprocts short, about equal to middorsal length of Ab9+10 -Boyeria

3b. Distalmargin of palpal lobes ending in curved tips (picture); no evidentspot on abdominal segment 8, and paraprocts longer, length greaterthan middorsal length of Ab9+10 - Basiaeschna janata

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4a.(2b). Low median ridge on dorsum of abdomen with blunthooks on Ab7-9 (picture); palpal lobe rounded at tip (picture) -Nasiaeschnapentacantha

4b. Low medianridge on dorsum of abdomen without blunt hooks on Ab7-9 (picture);palpal lobe truncate at tip (picture) - Epiaeschnaheros

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5a.(1b). Antennae longer than distance from their base torear of head (Figure 5a1); distal margin of ligula deeply bilobed,with a V-shaped notch (Figure 5a2) - Gomphaeschnafurcillata

Fig. 5a1:
Gomphaeschnafurcillata exuvia (6x, dorsalview), from tupelo swamp west of Walkertown, Hardin Co., Tennessee,collected on 01 April 1986 by K. J. Tennessen. Image from specimenkindly loaned by K. J. Tennessen.
Fig. 5a2: Ibid, (12.5x, ventral view).

5b. Antennaeabout half as long as distance from their base to rear of head(picture); distal margin of ligula obtuseangulate, at most veryslightly bilobed, with the notch closed (picture) - 6
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6a.(5b). Truncated blade of lateral lobe with prominent endhook (picture); compound eyes as long as their greatest width(picture); mentum 2 or more times as long as width at base (picture);paraprocts about equal to Ab8+9 (picture) - Anax

6b. End hooknot prominent (picture); compound eyes much shorter than theirgreatest width (picture); mentum < 1.5 times as long as width atbase (picture); paraprocts shorter than above, about equal to Ab9+10(picture) - Aeshna

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Corbet, P. S. 1962. Abiology of dragonflies. E. W. Classey Ltd.: Oxon, England. xvi + 247pp.

Walker, E. M. 1958.The Odonata of Canada and Alaska, Vol. 2. University of TorontoPress: Toronto. xii + 318.

Westfall,M. J., and K. J. Tennessen. 1996. Odonata, pp. 164-211.In AnIntroduction to the Aquatic Insects of North America, 3rd Ed.Merritt, R. W. and K. W. Cummins (eds.). Kendell/ Hunt PublishingCompany: Dubuque, Iowa.

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