CUIRONOMUS. 151 



The species of this genus are very numerous, and there are 

 probably many British kinds in addition to those here described. 

 They may be often seen hovering in the air in immense swarms, 

 particularly towards evening, and those with delicate colours do 

 not usually appear till near sunset. Some of the species with 

 short fore metatarsi run with great activity ; the others are more 

 slow in their movements. 



" The larva of C. plumosiis is abundant in stagnant water, and 

 is named Blood-worm on account of its colour, form, and move- 

 ments. Tlie head has two ocelli-like points, and two biarticulate 

 palpi. The first tlioracic segment has two short pediform ten- 

 tacles beneath. The anal segment is furnished with two large 

 and four small oval appendages, and there is a pair of long fleshy 

 filaments on each of the two preceding joints. The larva at the 

 bottom of the water forms tortuous tubes, which are composed of 

 particles of decayed leaves." 



" The pupa is not enclosed in a case, but is of a greater specific 

 gravity than the water, at the bottom of which it resides until 

 within a few hours of the exclusion of the fly. It has the power 

 of swimming, and by moving the tail alternately backwards and 

 forwards can slowly raise itself to the top of the water. For the 

 extrication of the imago it is necessary that it should remain 

 quietly suspended at the surface; and moreover that the thorax, 

 in which the o])ening for its exit is to be made, should be at least 

 level with it, and this is precisely what takes place. As soon as 

 it has reached the top it remains suspended there motionless, and 

 its thorax is the highest part of the body, and level with the sur- 

 face. The middle of the back of the thorax has the property of 

 repelling water, apparently from being covered with some oily 

 secretion. Hence, as soon as the pupa has once forced this part 

 of its body above the surface, the water is seen to retreat from it 

 on all sides, leaving an oval space in the disc, which is quite dry. 

 Just previously to the exclusion of the fly, tlie dry part of the 

 thorax is seen to split in the middle. The air enters, and forms 

 a brilliant stratum, resembling quicksilver, between the body of 

 the insect and its puparium; and the former, pushing forth its 

 head and fore legs, rests the latter upon the water, and in a few 

 seconds extricates itself wholly from its envelope. The pupa, for 

 respiration, has on each side of the thorax a pencil, consisting of 

 five hairs elegantly feathered, which, when they diverge, forms a 

 beautiful star ; its anus also is furnished with a fan-shaped pencil 

 of diverging hairs." 



" The grub of C. stcrcorarius inhabits horse-dung, and has a 



