. Fresh-water biology. Freshwater biology. AQUATIC INSECTS 891 There is much diversity of egg-laying habits in the order. All the damselflies and many dragonflies, especially Aeschnidae, are provided with an ovipositor, by means of which punctures are made in the stems of aquatic plants, in logs, in wet mud, etc., for the reception of the eggs. The eggs are placed singly in the punc- tures, and usually just below the surface of the water; but a few damselflies descend the stems to place them deeper, and some species of Lestes place them habitually in the stems above the sur- face. Here they ar
. Fresh-water biology. Freshwater biology. AQUATIC INSECTS 891 There is much diversity of egg-laying habits in the order. All the damselflies and many dragonflies, especially Aeschnidae, are provided with an ovipositor, by means of which punctures are made in the stems of aquatic plants, in logs, in wet mud, etc., for the reception of the eggs. The eggs are placed singly in the punc- tures, and usually just below the surface of the water; but a few damselflies descend the stems to place them deeper, and some species of Lestes place them habitually in the stems above the sur- face. Here they are subject to the attack of egg parasites. The females of those dragonflies that lack a well-developed ovipositor drop their eggs upon the surface of the water while in flight (usually descending to touch the surface, and thus to wash them free), whereupon the eggs scatter and fall to the bottom; or, they settle on some plant stem at the surface and hang them in gelatinous masses about the stem. In certain of the Cordulinae these masses are long gelatinous strings, containing many hundreds of eggs. It is easy to get the eggs of most Libellulines for study. When a fe- male is seen tipping the surface of the water with her abdomen while in flight, if she be captured uninjured and held by the tips of the fore wings (leaving the hind wings free) and dipped against the surface of the water in a glass, in imitation of her own motion while at large, she will usually liberate eggs in great abundance in the water. These require about three weeks for hatching, and the nymphs begin to eat each other early in life. There are nymphs of Odonata in all sorts of fresh water. Those of some of the larger active species clamber about freely among. Fig. 1361. Damselfly nymphs; a, Catopteryx; 5, Lestes. water weeds, and even chase their prey, creeping stealthily upon it imtil within range. Most damselflies (Fig. 1361) clamber about. Please note that these images are extracted from scanned page image
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
