INTRODUCTION. 13 



tropic or phaotropic, i.e. toward or away from the sun or 

 light, sometimes lateral, sometimes forward and backward. 



Other chrysalids are attached not only by the tail but 

 also by a girth, whether tight or loose, slung around the 

 middle of the body in the dorsal depression or saddle which 

 always exists between the thoracic and abdominal regions. 

 If the girth be tight, the ventral surface of the chr3'salis, 

 which touches the surface of rest, is nearly or quite straight ; 

 if loose, it is often bent to a greater or a less degree 023po- 

 site the girth, or describes a curve with the same point as 

 the middle of the arc. 



A modification of this mode of suspension is seen in some 

 Skippers, which make cocoons in which both the median 

 girth and sometimes to a less extent the tail attachments 

 form Y-shaped strands, which are attached at their ex- 

 tremities to the walls of the cocoon ; into the centre of one 

 set the hooks of tlie tail are plunged, while the middle of 

 the body is slung between the longer arms of the other and 

 larger set of strands. 



There is but one family of butterflies in which all the 

 members construct cocoons — the Skippers. Their cocoons 

 are usually of a rather fragile nature and consist (usually) 

 of leaves, blades of grass, or other vegetable material, gen- 

 erally living, shaped into a more or less oval or cylindrical 

 cell by silken attachments ; sometimes the interior is more 

 or less perfectly lined with a thin membrane of silk; within 

 this, as just stated, the chrysalis hangs by means of Y- 

 shaped shrouds, the form of the smaller one sometimes 

 difficult to determine from the mingling of its threads with 

 those forming the extremity of the cocoon. 



Chrvsalids which o:ive birth to butterflies the same sea- 

 son vary in their duration from about three days to a month, 

 but usually from ten days to a fortnight. But a consider- 

 able number pass the winter in this shape, and may then 

 endure from five to eleven months, and sometimes this lat- 



