 For moulting , all Portias spin a horizontal web whose diameter is about twice the spider 's body length and is suspended only 1 to 4 millimetres ( 0 @.@ 039 to 0 @.@ 157 in ) below a leaf . The spider lies head down , and often slides down 20 to 30 millimetres ( 0 @.@ 79 to 1 @.@ 18 in ) during moulting . : 496 Portias spin a similar temporary web for resting . : 513 Like all arthropods , spiders moult and , after hatching , the life stage before each moult is called an " instar " . The distinctive tufts of P. schultzi juveniles appear in the third instar . : 33 
