324 MOTIONS OF INSECTS. 



of these animals to the hairs upon their suckers'. That 

 learned and pious naturalist, Dr. Derham, seems to 

 have been one of the first who gave the true solution 

 of this enigma. " Flies," says he, " besides their sharp 

 hooked nails, have also skinny palms to their feet, to 

 enable them to stick on glass and other smooth bodies, 

 by the pressure of the atmosphere^ .'''' He compares 

 these palms to the curious suckers of male Dj/tisciy 

 before alluded to, and illustrates their action by a com- 

 mon practice of boys, who carry stones by a wet piece 

 of leather applied to their top. Another eminent and 

 excellent naturalist, the late Mr. White, adopted this 

 solution. He observes that in the decline of the year^ 

 when the mornings and evenings become chilly, many 

 species of flies retire into houses and swarm in the 

 windows : that at first they are very brisk and alert ; 

 but, as they grow more torpid, that they move with dif- 

 ficulty, and are scarcely able to lift their legs, which 

 seem as if glued to the glass ; and that by degrees many 

 do actually stick till they die in the place. Then no- 

 ticing Dr. Derham's opinion as just stated, he further 

 remarks, that they easily overcome the atmospheric 

 pressure when they are brisk and alert. But, he pro- 

 ceeds, in the decline of the year this resistance becomes 

 too mighty for their diminished strength; and we see 

 flies labouring along, and lugging their feet in windows 

 as if they stuck fast to the glass". 



Sir Joseph Banks, to whom every branch of Natural 

 History becomes daily more indebted, has lately ex- 

 cited an inquiry, the results of which have confirmed 



» iv. 259. " Physico-Theol. Ed. 13. 363, note b. 



"Nat. UisLii. 21^1. 



