SUPERFAMILY TINEOIDEA 117 



instars, the first three of which, so far as known are sap- 

 feeding. These relations are indicated in the table on 

 page 61. Certain details of the shift of form will be cited 

 in the account of particular species, such as Acrocercops 

 strigifinitella (see p. 124). 



The marked change in form between the earlier and later 

 instars is always associated with changes in habits. Most 

 forms become external feeders after this change. Their 

 newly acquired spinning abilities are brought into play in 

 bending the leaf into a roll, or cone, or fold for shelter, and 

 later in spinning cocoons for pupation. Among the Litho- 

 colletis allies there is always a distinct change in habit and 

 this change manifests itself differently in the various genera. 

 In Lithocolletis proper, after the third instar the larvae 

 cease extending the mine and begin going over the area from 

 which the cuticle has been freed, picking out the paren- 

 cyhma. They use their spinning abilities in causing the flat 

 mine to become tentiform by spinning silk across the loos- 

 ened cuticle, and drawing it into folds. The Lithocolletis 

 larvae of the flat type (the Cameraria group), which only in 

 part resume the cylindric form after the third moult, con- 

 tinue to extend the borders of their mines during two addi- 

 tional feeding instars, and then complete the change to 

 cylindric form, and remain quiescent during two non-feed- 

 ing instars, before transforming to pupae. Their spinning 

 powers are employed in the making of cocoons. 



In these later instars there is a gradation through the 

 Gracilariidae in the degree of development of legs. In the 

 external feeding stages the Gracilara and its near allies the 

 legs and prolegs have as great a development as in other 

 larvae that are free-feeding from birth. In some members 

 of the Lithocolletis groups they are fairly well developed. 

 In the fourth and fifth and even sixth and seventh stages 

 of the Cameraria group they are very little developed in- 

 deed, the thoracic legs often being reduced to mere disc-like 



