the honey-bee as to deceive the very elect. One of my stu- 

 dents, an enthusiastic collector and well acquainted with this 

 case of mimicry, oace grasped a bee in his hand, under the 

 impression that he was capturing one of these files. Now, 

 on any theory, we must admit that these species of flies are 

 of more recent origin than the species which they mimic. 

 Most of these imitative flies belong to the family Syrphidae, 

 which is considered to be one of the oldest of the group 

 Cyclorrhapha, comprising the higher flies. 



The Diptera, as a whole, are wonderfully rich in peculiar 

 modifications of structure. In almost any organ the variety 

 of forms exceeds that of any other order. Even the antennae 

 of beetles do not surpass, if they equal, those of flies in this 

 respect. The wings are far more variable in venation than 

 those of any other order. The variety and complexity of 

 organs for grasping the female are almost beyond belief to 

 one who has not seen them. 



The one thing which has prevented the recognition of the 

 real rank of the Diptera is a lingering notion that specializa- 

 tion by reduction really brings an insect down to a lower 

 position in the scale. The word "high" suggests the idea 

 of "complete," or "perfect," or "typical." If Professor 

 Hyatt's test were to exclude every other, as it ought to, there 

 could scarcely be any further disagreement on the question 

 of the highest order. 



The line of argument here suggested points to the Pupi- 

 para as the highest of all insects; nor would I in the least 

 seek to evade the conclusion. Of the group, I have seen 

 only the Hippoboscidse ; among these the sheep tick, Melo- 

 phagus ovinus Linn, appears to deserve the highest rank. 



J. M. Aldrich. 



