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Although there is so wide a difference in colour between the sexes of many Libellulidae, it is often difficult to say which is the more brilliant; and the ordinary coloration of the two sexes is reversed, as we have just seen, in one species of Agrion. It is not probable that their colours in any case have been gained as a protection. Mr.
Although many dragon-flies are large, powerful, and fierce insects, the males have not been observed by Mr. MacLachlan to fight together, excepting, as he believes, in some of the smaller species of Agrion.
The labium is not developed from a pair of tubercles, as is usual, but at once appears as an unpaired, or single organ. The pupa state lasts for five or six days, and when the imago appears it eats its way through a small round opening in the end of the skin of its host, the Agrion larva. The development of Ophloneurus, another egg-parasite, agrees with that of Platygaster and Polynema.
MacLachlan, R., on Apatania muliebris and Boreus hyemalis; on the anal appendages of male insects; on the pairing of dragon-flies; on dragon-flies; on dimorphism in Agrion; on the want of pugnacity in male dragon-flies; colour of ghost-moth in the Shetland Islands.
There are a thousand concealed fitnesses in nature, rhymed correspondences of bird and blossom, for which you must seek through hidden paths; as when you come upon some black brook so palisaded with cardinal-flowers as to seem "a stream of sunsets"; or trace its shadowy course till it spreads into some forest-pool, above which that rare and patrician insect, the Agrion dragon-fly, flits and hovers perpetually, as if the darkness and the cool had taken wings.
The English entomologists assert that the female Agrion goes below the surface to a depth of several inches to deposit eggs upon the submerged stems of plants." The Agrions, however, according to Lucaze Duthiers, a French anatomist, make, with the ovipositor, a little notch in the plant upon which they lay their eggs. These eggs soon hatch, probably during the heat of summer.
MacLachlan informs me of another instance of dimorphism in several species of Agrion, in which some individuals are of an orange colour, and these are invariably females.
The Libellulidae, or dragon-flies, are ornamented with splendid green, blue, yellow, and vermilion metallic tints; and the sexes often differ. Thus, as Prof. But in Agrion Ramburii these colours are exactly reversed in the two sexes. Walsh, ibid. p. 381. In Anax junius the basal part of the abdomen in the male is a vivid ultramarine blue, and in the female grass-green.
This is probably a case of reversion; for in the true Libellulae, when the sexes differ in colour, the females are orange or yellow; so that supposing Agrion to be descended from some primordial form which resembled the typical Libellulae in its sexual characters, it would not be surprising that a tendency to vary in this manner should occur in the females alone.
Digits, supernumerary, more frequent in men than in women; supernumerary, inheritance of; supernumerary, early development of. Dimorphism, in females of water-beetles; in Neurothemis and Agrion. Diodorus, on the absence of beard in the natives of Ceylon. Dipelicus Cantori, sexual differences of. Diplopoda, prehensile limbs of the male. Dipsas cynodon, sexual difference in the colour of. Diptera.
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