Fig. 4:9. Copulation of Macromio magnified (Kennedy, 1915). 



emerges through a slit in the dorsum of the head 

 ind thorax. 



The newly emerged adults are pale and without 

 the darker markings. Within a few hours the pattern 

 appears, but the full color does not develop until 

 later. Blues and reds are especially slow to develop. 

 Different kinds of Odonata have characteristic flight 

 and habits. Details are given below under the special 

 discussions. 



In general, the dragonflies have very few natural 

 enemies. The teneral adults are especially vulnerable 

 owing to their weak powers of flight. At this time and 

 later they may be attacked by birds, lizards, frogs, 

 spiders, and other Odonata. The naiads are eaten by 

 fish, birds, frogs, and other aquatic insects. Of these 

 the most important are the fish. A few hymenopterous 

 egg parasites have been reported on some of the 

 ispecies that lay their eggs in plant tissue. The 

 [parasite goes beneath the water to oviposit in the 

 |eggs. Certain water mites are also occasionally 

 ; abundant on the naiads. 



Adult dragonflies are usually collected with a 

 standard insect net. The net opening should be 

 fifteen inches or more in diameter and the handle 

 at least three feet long. In netting a dragonfly, a 

 quick following stroke from below and behind is 

 better than a head-on stroke. Many species have 

 regular habits of flight and their movements can be 

 anticipated. In some cases sweeping vegetation in 

 the early morning or at night will be very profitable. 

 For damselflies a large fly swatter is helpful and 

 for large, high-flying forms the finest dust shot in a 

 .22 target pistol will yield a fair proportion of good 



109 

 Smith and Pritchard: Odonata 



specimens. Rearing the adults from the naiads fre- 

 quently gives the best specimens and, of course, 

 associates the two stages. 



•The adults should not be killed in cyanide hut 

 papered and allowed to die slowly. When handled in 

 this manner the contents of the gut are excreted and 

 the colors of the preserved specimens are at their 

 best. Artificial drying is sometimes necessary to fix 

 the colors properly. The adults may then bo pinned, 

 or better, placed with wings folded in transparent 

 envelopes, or they may also be placed directly into 

 80 per cent alcohol. 



Naiads may be collected by any of the usual aquatic 

 insect collecting methods. They should be preserved 

 in 80 per cent alcohol. 



Key to Nearctlc Families 



Adults 



1. Fore and hind wings dissimilar in size and shape, the 

 proximal part of hind wing broader than that of fore 

 wing; supratriangle and triangle present (fig. 4:2); 

 male with 3 caudal appendages — 2 superior and 1 

 inferior (fig. 4:32) ANISOPTERA 2 



— Fore and hind wings similar in size and shape, the 

 proximal part of both fore and hind wings of about equal 

 width (fig. 4:74); quadrangle present; male with 4 

 caudal appendages — 2 superior and 2 inferior (fig. 

 4:60) ZYGOPTERA 6 



2. Triangles of fore and hind wings about equally distant 

 from arculus and similarly shaped (fig. 4:6a) 3 



— Triangle more distant from the arculus in fore wing 

 than in hind wing and with its long axis at right angle 

 to costa (fig. 4:66) L1BELLULIDAE 



3. Stigma with a brace vein at its inner end (fig. 4:4) 



: 4 



— Stigma without a brace vein at inner end (fig. 4:2) 



CORDULEGASTRIDAE 



4. Eyes widely separated on top of head 5 



— Eyes meeting on top of head or nearly so 



AESHNID AE 



5. Stigma linear, not widened medially (fig. 4:15) 



PETALURIDAE 



— Stigma rhomboid, widened medially (fig. 4:4) 



GOMPHIDAE 



6. Wings distinctly petiolate, with 2 to 4 antenodal cross 

 veins (figs. 4:616, c; 4:74) 7 



— Wings not distinctly petiolate, with 5 or more antenodal 

 cross veins (fig. 4:61a) AGRIONIDAE 



7. Wings with vein M s arising nearer to arculus than to 

 nodus; short intercalary veins present between M s and 

 principal adjacent veins and running to wing margin 

 (fig. 4:616) LESTIDAE 



— Wings with vein M s arising nearer the nodus than to the 

 arculus; no such intercalary veins present (fig. 4:61c) 



COENAGRIONIDAE 



Naiads 



1. Anus surrounded by 3 stiff pointed valves (fig. 4:13); 

 head not markedly wider than thorax and abdomen (fig. 

 4:10p) ANISOPTERA 2 



— Three external gills present at caudal end of abdomen; 

 head wider than thorax and abdomen (figs. 4:14; 4:72) 



ZYGOPTERA 6 



2. Mentum of labium (including lateral lobes) flat, or 

 nearly so, without stout setae 3 



— Mentum of labium (including lateral lobes) spoon- 

 shaped, covering face to base of antennae (fig. 4:10?), 

 armed with stout setae (fig. 4:11/) 5 



3. Antenna 6- or 7-segmented (fig. 4: 11a, 6); tarsi 3-seg- 

 mented, the fore tarsus 2-segmented in Gomphaeschna 

 4 



