Anax Leach, 1815 - Green Darners

Fig. 1: Anax longipes
Larva collected from the ESGR, Livingston Co., Michigan, USA

The genus Anax is widespread in temperate and tropical regions of the world. Four species are found in the New World, two of which are found in Michigan (Map 1-2). These are large nymphs found in still waters (ponds, lakes and still portions of streams) clinging to aquatic vegetation.

Map 1Map 2
Michigan county distribution of A. junius (map 1) and A. longipes (map 2).
Click on map for a larger image.

A. longipes (Fig. 1) recently has been added to Michigan's Odonata list (Kielb and O'Brien 1997), with a thriving population found in several experimental, fishless ponds at the University of Michigan's E. S. George Reserve in Livingston County, southeastern Michigan (Map 2). Among our largest odonate larvae, mature nymphs exceed 60 mm in total length. Emergence from this site appears to occur from mid-June through early August (Figure 2).

Figure 2: Exuvia of Anax longipesi on cattail (Typha latifolia) from an experimental pond at the
E. S. George Reserve, Livingston County, Michigan.

A. junius is a common resident of small and large lentic habitats throughout Michigan where fish predation is not a significant factor. I have also found them in very slow-moving waters with ample aquatic vegetation in slow-moving stream waters. Apparently two populations with different emergence periods exist in the northern part of its range (Trottier 1966, 1971). One (non-resident) population apparently migrates northward to oviposit in spring, with larvae rapidly developing until a September emergence, subsequently with newly emerged adults migrating southwards. Another cohort apparently stays year-round, with ovipositing occurring in July, with some egg diapause and subsequent larval development during winter and spring until a June emergence. Work should be done to determine whether these populations can be genetically distinguished.

Other links with information on the biology or ecology of larval Anax:
none found as of 20 January 1998

1. Total length of mature nymph >60 mm; folded labium passes metacoxa towards first abdominal segment (Fig. 2); labial lobes clearly truncated (Fig. 3) - A. longipes

Fig. 2Fig. 3
Fig. 2-3. Anax longipes exuvia, collected by M. Kielb as larva on 06 August 1996, with adult emerging on 14 August 1996. From the E. S. George Reserve, Livingston County, Michigan. UMMZODO-1811.

1a.Total length of mature nymph <55 mm; folded labium clearly does not reach beyond metacoxa (Fig. 4); distal edge of labial lobes somewhat rounded (Fig. 5) - A. junius

Fig. 4Fig. 5
Fig. 4-5: Anax junius, collected from Long Lake in Newago Co., Michigan, on 11 September 1926 by T. H. Langois & P. A. Moody. UMMZODO-1307.

Drury, D. 1773. Illustrations of natural history. Vol. 2. White: London. 90 pp.

Hagen, H. A. 1861. Synopsis of the Neuroptera of North America, with a list of the South American species. Smithsonian Miscellaneous Collections 4:1-347.

Kielb, M. A., and M. F. O'Brien. 1997. Discovery of an isolated population of Anax longipes in Michigan (Odonata: Aeshnidae). Great Lakes Entomologist 29(3):161-164.

Leach, W. E. 1815. Entomology, pp. 52-172. In Brewster's Edinburgh encyclopaedia. Vol. 9. Edinburgh.

Needham, J. G., and H. B. Heywood. 1929. A Handbook of the Dragonflies of North America (Anisoptera). C. C. Thomas: Springfield, Illinois. 378 pp.

Needham, J. G., and M. J. Westfall. 1955. A Manual of the Dragonflies of North America (Anisoptera). University of California Press: Berkeley, California. x + 615 pp.

Trottier, R. 1966. The emergence and sex ratio of Anax junius Drury (Odonata: Aeshnidae) in Canada. The Canadian Entomologist 98:794-798.

Trottier, R. 1971. Effect of temperature on the life-cycle of Anax junius (Odonata: Aeshnidae) in Canada. The Canadian Entomologist 103:1671-1683.