that prey on the lesser genera, have prevented such an increase of them as to become in a little time a plague too great to be borne? No. The Almighty Creator has most wisely constituted this genus for executing His commands in the manner I have described; and for this reason they must be considered as beings of greater consequence than the inconsiderate part of mankind allow them to be. "Nor is this the only advantage arising from their existence. The still waters, where these creatures are inhabitants during their infant state, are in some degree by their assistance preserved sweet and good, that otherwise might corrupt and putrify, for the motion the waters receive by these insects is not trifling; the respiration they perform in that element being observable by a close attention, which, together with that and the motion of thousands of other insects, does in some measure contribute to keep it sweet and wholesome." PLATE XLVII. [Illustration] LIBELLULA LYDIA. Plate XLVII. fig. 4. ORDER: Neuroptera. SECTION: Subulicornes. FAMILY: Libellulidæ, _Leach_. GENUS. LIBELLULA, _Linn. &c._ LIBELLULA LYDIA. Subænea, abdomine ([male]) coeruleo lateribus luteis, alis hyalinis, singulâ strigâ parvâ basali fasciâque latâ transversâ pone medium, fusco-chalybeis. (Expans. Alar. 2 unc. 9 lin.) SYN. Libellula Lydia, _Drury, App. vol._ 2. HABITAT: Virginia. Front of the head green. Eyes dark brown, very large, and placed near each other. Thorax green, having on each side two transverse yellow stripes. Abdomen of the male blue, with small yellow indented marks on the sides; that of the female yellow; the former having two little horny substances like tails at the extremity, which are wanting in the female. Wings reticulated and transparent; the middle of each being of a very dark blue colour, occupying about a third part, and crossing them from the anterior to the posterior edges, which by the reflection of white paper becomes dark brown. A dark brown stripe also, about a quarter of an inch in length, issues from the base of each wing, almost joining to the anterior edge; below which the males have a white patch placed on their inferior wings. ÆSHNA JUNIA. Plate XLVII. fig. 5. ORDER: Neuroptera. SECTION: Subulicornes. FAMILY: Libellulidæ, _Leach_. GENUS. ÆSHNA, _Fabr._ Libellula, _Linn. &c._ ÆSHNA JUNIA. Fuscescens, unicolor (in vivis virescens?), alis hyalinis, costâ pallidè infuscatâ, stigmate oblongo, nigro. (Expans. Alar. 4 unc. 3 lin.) SYN. Libellula Junia, _Drury, App. vol._ 2. HABITAT: New York.