THE BED-BUG 293 



While in the nymph condition the bug is still just as 

 active as before, and continues to take food with equal 

 readiness. At length the final moult occurs, and the 

 insect is sexually mature, and acquires its rudimentary 

 elytra, or upper wings. No further growth takes place, 

 as, owing to the inflexibility of the skin, this can only 

 be effected by moulting. The food now taken, therefore, 

 serves not for increase of bulk, but to maintain the 

 proper balance of the activities of the body, and to supply 

 materials for the perfecting and discharge of the repro- 

 ductive functions. The insect is said to require in all 

 about eleven weeks to reach maturity, but the exact 

 duration of its metamorphoses is no doubt greatly 

 dependent upon the regularity and amount of the supply 

 of food. In the adult condition it can certainly endure 

 long fasts with impunity. De Geer kept several in a 

 sealed bottle for more than a year without food. It is 

 also a well-known fact that bugs sometimes absolutely 

 swarm in houses that have for a long time been un- 

 inhabited. In such cases it is obvious that they have 

 managed to exist without access to human blood ; still 

 it does not necessarily follow that they have been entirely 

 without food of any kind ; and when we remember that 

 their human parasitism is probably an acquired habit, 

 their appearance under such conditions will be less 

 difficult to understand. 



It has been supposed that they are able to abstract 

 juices sufficient to support life from the woodwork of 

 buildings ; and if we take into consideration the absorp- 

 tive properties of unpainted soft woods, such as deal, it 

 seems far from incredible that such may be the case. 

 That an insect which has been accustomed, during the 

 greater part of its individual life, to subsist upon animal 

 matter, should suddenly change its diet and feed upon 



