NO. 2242. MORPHOLOGY OP THE 8TREP8IPTEBA— PIERCE. 419 



ranged with them if they exhibited a perfect agreement in charac- 

 ters. They do not agree with any part of the Coleoptera in their 

 characters. Therefore by Rule IV the Strepsiptera are an order. 



Rule V. When insects formerly placed arbitrarily in some of the 

 older orders are found hy paleontology to he a distinct line of de- 

 scent from the order with which they have been ranked, and show 

 deckled difference from this order in structure or in metamorphosis, 

 they should be separated out to form a new order. 



In converse: Insects which should be separated from an older 

 order in accordance with any of the preceding rules, and yet which 

 show a common origin, must also constitute a new order. 



The Strepsiptera are at least Tertiary in age, and possessed in 

 that period all of the essential characters which so well distinguish 

 them now from other orders. The geographic distribution of the 

 group, in every faunal zone of the globe, especially their occurrence 

 in the South Seas, in Australia, and the Malay Archipelago, is evi- 

 dence of a very ancient origin. It is of great interest that the most 

 primitive superfamily contains representatives in Australia, Algeria, 

 Mexico, and Germany. 



No group of insects has yet been found with which the Strepsiptera 

 can be associated phylogenetically. They stand alone' in their pe- 

 culiar structure and habits. 



The evidence therefore is all for their separation as a distinct order. 



The assemblage of characters which distinguish the order may be 

 summarized below. It must be understood that analogies may be 

 found to many of these characters singly, but that the combination 

 nowhere else is to be found. 



CHAEACTEKISTICS DISTINGUISHING THE ORDER. 



Morphological characters. 



1. Dissimilarity of sexes, the male winged, hexapodal, active; the 

 female blind, wingless, legless, inactive. 



2. A regular sequence of structural modifications from primitive 

 to highly specialized, is observable throughout the order, paralleling 

 yet not approaching similar evolutions in other orders, and in some 

 ways more remarkable. 



3. The male thorax, which is undoubtedly the most important 

 ordinal character, is absolutely different from the thorax of all 

 other orders. The thorax of Myodites solidaginis, a Rhipiphorid, 

 is shown in plate 69, figures 4, 5. This is the only Coleopterous 

 family which any author has tried to ally to the Strepsiptera. 



a. The protliorax and mesothorax are both greatly reduced, and the meta- 

 thorax is preponderant. This is the only group of insects in which the 

 metathorax has received the preponderance of size. Certain Coleoptera 

 have a greatly enlarged metathorax but they also have the prothorax 



