156 



EVENINGS AT THE MICROSCOPE. 



THE SUCKER OF A BUTTERFLY. 



A small portion of one half- 

 cylinder. 



and completeness, is a process dependent on respiration, 

 and connected with the air-pipe that permeates each divi- 

 sion of the sucker.* 



It will not be a very violent 

 transition if from the sucking- 

 pump of the Butterfly I carry you 

 to the silk- spinner of the Cater- 

 pillar. Here I have a Silkworm 

 in the act of commencing its 

 cocoon ; by inclosing which in this 

 glass tube we shall conveniently 

 have the insect at command, and 

 shall be able to view the process 

 under a low magnifying power and- 

 reflected light. Now the grey face 

 of the worm is presented to us ; 

 and we can see, below the edge 

 of the head- shield, a short broad 



upper lip, forming two blunt points. Below this is the 

 pair of strong brown mandibles, convex outwardly and 

 concave inwardly, each cut at its broad biting edge into 

 several teeth. Below these are two little points which 

 represent the maxilla, and between them a blunt rounded 

 knob, which is the lower lip (labium). 



You may also see on each cheek, close to the base of 

 the mandible, a little pit, out of which rises a short 

 columnar organ tipped with two bristles ; these columns 

 are the incipient antenna. Outside them you may dis- 

 cern, on each cheek, a series of six globes of glass (so 

 they appear) set in the substance of the skin } five 

 forming a semicircle, and one in the centre ; these are 



* Mr. Darwin, in his admirable work On the Fertilisation of Orchids, 

 p. 33 et seq., has shown that the tubular proboscis of Lepidoptera, 

 while used by the insect solely for the collection of nectar, is indirectly 

 and unintentionally used for the transferring of pollen-grains from 

 flower to flower ; and thus becomes a most important agent in the pro- 

 pagation of plants. (See his remarkable figure on p. 37 op. cit.) 



