INSECT VARIETY. 97 



jealous and pugnacious in relation to the bravery of their lines. 

 This temperament has its maximum in summer on warm, moist 

 spots, or as we approach the tropic zones, where torrid skies 

 drive and locate the various species on the borders of pools and 

 streams, and where, eollecting in thirsty groups, they rise ever and 

 anon in air, and whirl in variegated garlands round and round, 

 with rapid rush of wings, like the rustling autumn leaves. 

 Such butterfly waltzes form alike a prelude to pairing and 

 migration. 



Of aerial dances now noticed, vertical figures, or hovering, 

 where species are virtually mute, seem specially to illustrate 

 conditions of attraction by reflection, colour, or luminosity ; 

 and in this way the pale colour of the longhorned nocturnal 

 NemophoTfe, and sexual differentiation indicated in the genus 

 ■ Repialus, the metallic gloss on the wing-scales of AdeUv, or opal 

 refractions on the membranous wings of May Flies {Triclioptera 

 and Tipnlida), whether arising from notched scales, hair, or 

 wing surface, or emanating from dermal glitter of gem-like 

 abdomens, as in the case of sun-poised Hover Flies, and 

 sedentary Dragon Flies, all severally fulfil the conditions of 

 display, as does in like measure the leaping spangle of the 

 Fire Flies. But in the dances of bees, flies, and beetles Ave 

 witness commingling another element, and this especially as 

 their curves of motion approximate horizontality, so that cases 

 occur Avhere the tensive qualities of sound appear to replace 

 those of light. The circular dances, which especially exhibit 

 this feature of vocal music, if primarily dependent on wing 

 outline, in many Lamellicornes appear exaggerated by the 

 horizontally-extended hollow elytra, which seem to render in- 

 trinsical that wheeling or curvilinear horizontal path we see in 

 Dung Beetles,^ a feature by no means general, for others of this 

 tribe hardly expand the wings, as the Eose Beetles, and some raise 

 them vertically over the back, as the Burying Beetles. Aerial 

 display exhibits one common feature— it is enacted in the wind's 

 eye; aerial migration, it can be shown, on the contrary, takes 

 direction from the wind. 



The sense directly corresponding with display is sight. The 



* They can, however, fly in a straight line. 



