DRAGON-FLY. Any amphibious insect of the order Odonata. These insects possess nu merous popular names, such as snake-feeder. horse-stinger, spindle, devil's darning-needle, and mosquito-hawk. They have ve very large heads. due to the exee-sive size of the eves: the anten me are short and the biting mouth-parts are pow erful; the four wino, are of -Millar size and structure; the legs are long and used for perch ing rather than for crawling. Two distinct types of dragon-tlies are now recognized : ( ) Zygop tera, whose wings. in repose. are held upright and (2) Anisoptera, whose wings are held hori zontal. To the former group belong our common slender-bodied blue form• sometimes called damsel-flies, while to the latter belong our larger and usually more sombre species. Both kinds are most frequently found about ponds. marshes, or streams, but some forms go a considerable dis tance from water, in meadows. in sunny hours. where they hawk for small insects with exceeding speed and voracity. The Zygoptera fly nearer the ground and more among vegetation than do the Anisoptera. Dragon-flies are known to swarm, both in America and in Europe. but the causes of these migration, are unknown. Although harm less, these insects are much feared by persons un acquainted with them, which explains some of the strange names and accounts for the quaint beliefs that exist among the country people, who say that if a 'darning-needle' gets into your hair most disagreeable things will happen. the least of which is the sewing up of the ear.. The folk-lore of Europe, the Orient. and Japan abounds in superstitions and sayings in regard to these quite innocent but fierce-looking insects.
The reproductive habits of dragon-tlies are unique, in that there is no direct transference of the sperm from the genital ducts to the female, as in other insects. The sperm. previous to the transference, is stored in an accessory receptacle near the base of the male abdomen. The clasping attitude= are also peculiar. The male grasps the neck of the female by means of a pair of forceps at the end of the abdomen. the female then bends forward the apex of her abdomen to the aeeessory sperm-receptacle near the base of the male's ab domen, and thus the actual transference of the sperm take= place. Among the Zygoptera the pairs often fly about tandem-like. the male clasp ing the neck of the female: and in some species tne male may even retain his hold and accompany her when the female crawls beneath the surface to oviposit. The which go beneath the surface are those which oviposit in the tissues of plants. In some dragon-tlies the egg. are dropped or washed off of the abdomen by dipping it into the water or striking it upon the surface. Larva- of Odonata are called 'nymphs.' and are aquatic and carnivorous. The lower lip is greatly developed and forms a powerful grasp ing organ. The zygopte ran nymph. have three
plate-like gill. al the end of the abdomen, while in the anisopteran nymphs respiration takes place in the greatly modified posterior part of the intestine into which water is drawn, and may be expelled with force sufficient to aid in loeomotion. in the zygopteran genera Euph:ea and Aniso pleura the nymph- also possess. in addition to the terminal gill-. lateral abdominal gills. Certain kinds of nymphs show ilecided preferences for cer tain habitat-, some choosing standing water, others small streams, and -till others rapid water. These preferences are a, marked as in the ease of the particular places frequented by the adults.
When a nymph is fully grown it crawls out of water and attaches it-elf. by means of its claws, to some support. The nymph-skin then split, along the top of the head and down the back, and through this rupture the imago escape-. At first the holy and wing. are limp and contracted, and only gradually expand to their full size; but the adult colors (I.) appea r for several hours, or even days. after emergence. The duration of the life of the imago varies from about three to six weeks for many form., but in the ease of those few forms which hibernate the limit may even extend over six month-.
While the dragon-tly. on account of its preying upon small insects and mosquitoes, is considered beneficial, the nymph-, on the other hand, have been credited with destroying young fish in hatch eries. While small insects doubtless form the bulk of their food, the larger -pecie, do not hesi tate to attack even wasps and butterflies.
The greatest extremes in size are found among the slender-bodied Zygoptera. The smallest is a .Javanese specie. (igriornemis minima). whose abdomen is about half an inch long, and the larg est is Megoloprepus ea-ralaHls, front Central America. whose abdomen is four inches long. A very large anisopteran (Gynacantha plagiata). from Borneo and Sumatra, has an ab domen nearly equal the latter in length.
About 2100 species of Odonata are known, the most of which are from tropical countries; but about 300 species occur in North America.
Fossil dragon-tlies. of which at least 75 species have been described. appear first in the Lia,, where they present already a considerable differ entiation, the majority of subfamilies being rep resented iu the rocks of that period. 111 the Ju rassic limestones of Solenhofen. Bavaria. occur numerous examples. mostly of extinct genera, that are often preserved in the finest manner, with the wino, spread out. Dragon-ffies are also found in all the Tertiary insect-bearing beds, and the larva- and pupa- occur in great abundance at Oening.en. Germany. See NEVROPTERA.
See DAMSEL-FLY and Plate of DaAoox-FLIER and DAMSEL-FLIEs.