20 INSECT MISCELLANIES. 



produced by moist air on their organs of touch, or 

 whether it arises from the diminution of hght upon 

 their eyes, we cannot tell. 



That it is not the quantity of Hght alone which 

 regulates the movements of many insects by day or 

 by night, appears from several facts. Some insects, 

 for example, appear only during particular hours of 

 the day, though the light before and after is much 

 the same. We have thus observed that the clouded 

 yellow butterfly {Colias Echisa) does not fly before ten, 

 and goes to rest soon after four o'clock. * The red 

 underwing moth {Catocala JVtqyta, Schrank), again, 

 has always been observed only about six or seven 

 o'clock in the morning, and never at any other time. 



Some of the smaller beetles {Hoplicc) are only to 

 be observed swarming before noon, when they all 

 disappear ; | as do most of the gnats, after dancing 

 for an hour or two at sunset. That these movements 

 are rather periodical than depending on either the de- 

 gree of light or heat, is rendered probable by close 

 analogies derived from plants. The Star of Bethle- 

 hem {Ornithogalum umbellatum), for example, ex- 

 pands its flowers about eleven, and closes them at 

 three in the afternoon, displaying its beauties about 

 two hours less than the clouded yellow butterfly. 

 The goats' beard {Tragojyogon pratensis) is still more 

 remarkable from closing its petals at mid-day, and 

 hence its provincial name of Go-to-bed-at-noon. That 

 light, however, is one of the most common agents 

 of these changes appears from the ingenious experi- 

 ments of Decandolle, made at the Jardin des Plantes 

 in an underground cellar, illuminated by lamps giving 

 a light equal to fifty-four ordinary wax candles. By 

 lighting these lamps he was able to produce the 

 opening of the flowers of the Star of Bethlehem at 

 pleasure, and also of the sea chamomile {Anihemu 



♦ J. R. t Linn. Trans, v, 256. 



