xxxii. '21] ENTOMOLOGICAL NEWS 117 



Larval and pupal characters are only of value within certain 

 limits in determining relationships. Where larval characters 

 contradict the evidence of the imago, they are of little or no 

 value. In the case of free-living larvae, adaptations develop 

 in the course of the struggle for existence. In insects with 

 complete metamorphosis, the habits of larva and adult may 

 differ widely, and hence the modifications of the larva may be 

 entirely independent and of no value in classification. Thus, 

 one only of two related organisms may have a specialized 

 larval stage or the same adaptation may have been added 

 independently in different groups to meet similar conditions 

 of environment. The use of pupal characters is perhaps open 

 to less serious criticism than the use of larval characters, as the 

 pupa is less obviously adaptive ; but it must be remembered that 

 the pupa is an interpolated stage, due to the differences be- 

 tween larval and imaginal habits. 



Larval and pupal characters often afford valuable confirma- 

 tory evidence in classification. For example, the similarity 

 of the pupae of the Micropterygidae and the Trichoptera, 

 confirms the conclusion of their near relationship based on 

 adult structure. Where a larval character is not liable to 

 change in evolution, and has been handed down through a 

 group without change, for example, the fourteen-legged larva 

 of the (jracilariidae, it can be used as a diagnostic character 

 in placing a form in that group, where the Cither characters 

 are not decisive. Even such a character must be used with 

 care, as it may be retained in several groups merely as an 

 inheritance from a common ancestor, and the adults may have 

 diverged so far from one another that they would never be 

 placed together except on larval characters. 



Apparent similarity and consequent apparent relationship 

 may result in errors of classification unless due regard be paid 

 to the course of evolution before taking the final result as a 

 basis of comparison. The placing of Opostcga close to Neptt- 

 citla is an example ; while they have 1 certain characters in 

 common, the course of evolution in vein reduction has been 

 totally different. It may be mentioned here that specimens of 

 OpostCflti may be found in which the- cell is faintly outlined 

 and additional veins present in the fore wing, showing clearly 



