Speaking of certain representatives of the Hymenoptera (_Chalcididae_), Mr. Westwood observes: "A curious peculiarity exists in one at least of these apterous species, which has been noticed by no previous author, namely, _Choreius ineptus_, Westw., which, although ordinarily found in an apterous state, was discovered by me in considerable numbers during the hot summer of 1835, with wings[15]". And, touching the irregularity of the alary organs in the Homopterous _Fulgoridae_, he remarks: "Other instances, in which the wings undergo a deficiency of development, occur in the genus _Delphax_, the majority of which, in our English species, have the upper wings not covering more than one half of the abdomen,--the terminal membrane being deficient, _as well as the hind wings_. In certain seasons, however, especially hot ones, the wings are fully developed[16]". Mr. Curtis has indeed formed the undeveloped specimens into a different genus, _Criomorphus_. Although the result of a more stimulating sun may be often neutralized by that of _isolation_ (which, as we shall hereafter see, is a resistless agent, amongst a host of species, in weakening, and frequently rendering abortive, the powers of flight); yet _heat_, when freed from counter influences, may be traced in its _permanent_ effect on the alary system of insects, no less than when temporarily applied. The consideration of this, however, belongs strictly to the preceding pages, and we will not therefore discuss it here. The common Bed-bug (_Cimex lectularius_, Linn.) is almost invariably apterous, or with very short rudimental hemelytra; yet Scopoli (_Ent. Carn._ p. 354) mentions its occurrence with perfect wings. Fallen, also, and Latreille, state that it has been found winged; whilst Westwood remarks that it has been reported as occasionally winged in the East Indies; and it would seem extremely probable that, in these examples, as in numerous others which are on record, we may detect the consequences of heat; either as temporarily applied (in an unusual degree), or through the accidental transportation of the insect into a naturally warmer atmosphere. Sec. III. _Nature of the country and of the soil._