CH. XV.] SPECIES OF DIPTEROUS INSECTS. 229 



it produced must have been truly formidable, threat- 

 ening, in fact, the total abolition of the culture of 

 wheat. So great, indeed, was the general dread of 

 the ravages of this fly, that the British Privy Council 

 sat daily for the purpose of considering the means 

 best adapted for guarding against the importation of 

 so formidable an enemy, and the account of their 

 deliberations occupies not less than two hundred 

 pages. It is moreover stated that " their numbers 

 were so incredibly great, that in wheat-harvest the 

 houses swarmed with them, to the extreme annoy- 

 ance of the inhabitants ; they filled every plate or 

 vessel that was in use, and five hundred were 

 counted in a single glass tumbler exposed to them 

 for a few minutes, with a little beer in it." 



The midges, belonging to the same Linnaean genus 

 as the wheat-flies, Tipula, afford another striking 

 example of the almost infinite number of individuals 

 produced in certain situations, belonging to a single 

 species. To these insects the name of gnat has 

 often been applied, but it appears to us that it would 

 be more proper to restrict that name to the insects 

 composing the Linnaean genus Culex, whose biting 

 propensities are so well known. 



Like the Ephemerae, of which they seem to be 

 the counterparts, these midges may be seen, espe- 

 cially in serene sunny evenings, assembled in vast 

 troops, alternately rising and falling in the air, so as 

 to exhibit one of the most pleasing spectacles. 

 These dances are kept up from about an hour before 

 sunset until the dew begins to fall. Messrs. Kirby 

 and Spence have described a beautiful scene exhibited 

 by these insects, accompanied by ephemerae, which 

 swarmed in infinite myriads, and appeared in the 

 sunbeams as numerous and more lucid than the 

 drops of rain, and as if the heavens were shower- 

 ing down brilliant gems. At another time, from 

 some cause in the atmosphere, the insects at a dis- 

 tance looked much larger than they really were, the 



VOL. II. U 



