April 30, 1897.] 



SCIENCE. 



673 



peculiarities and even intensifying them in 

 all future subdivisions to the present time. 

 In the first of these the prothorax, bearing 

 no wings, became separated from the other 

 rings and movable, or in a sense domi- 

 nant. In both the others it tended to a re- 

 duction in size or to become agglutinated 

 with or united to the others. In a general 

 way it may be said that the series in which 

 the prothorax is free is lower in the scale 

 of development, as retaining a more primi- 

 tive type. The orders belonging to this 

 subdivision or branch are the Dermoptera, 

 Coleopfera, Plecoptera, Platyjitera and Orthop- 

 tera. 



If we examine this series as a whole sev- 

 eral characters will be found to challenge 

 attention : First, a series of similarities in 

 the mouth structure. Omitting the Coleop- 

 tera and Flatyptera, which are most highly 

 specialized, all the others agree in the gen- 

 eral structure of the labium. In the Earwigs, 

 Stone-flies and Eoaches a divided ligula is 

 quite usual, and throughout the Orthoptera 

 glossa and paraglossa are usually separate 

 and even jointed. In the maxilla of all the 

 orders the lacinia may be said to dominate 

 and the galea tends to become rather a sub- 

 ordinate, often palpiform structure. There 

 are numerous exceptions to this in the 

 Coleoptera to answer special requirements, 

 but I believe that, as a whole, my state- 

 ment is correct. The maxilla tends to the 

 exercise of mandibular functions, and the 

 lacinia is the sclerite armed and modified 

 for the chief labor. Throughout this entire 

 series of orders the head is fairly well set 

 into the prothorax. There is no develop- 

 ment of a distinct neck between the head 

 and the first thoracic segment, and in many 

 cases the head can be almost entirely with- 

 drawn into the prothorax. This is an im- 

 portant feature which, so far as I am aware, 

 has not been suflBciently valued. In wing- 

 structure the secondaries dominate through- 

 out, and the uniform tendency is to a re- 



duction in size and loss of function in the 

 primaries. Furthermore, the wings lie flat 

 upon the back, and the secondaries are 

 folded under the primaries. To this struc- 

 ture of the wings, and the method of carry- 

 ing and folding them, I attribute much 

 weight, for it seems to me that, combined 

 with the other characters of head and 

 thorax, it argues a community or origin and 

 a separation from those forms differing in 

 these features. 



Among the most primitive in this series 

 are the Orthoptera, of which the roaches and 

 walking sticks are the most generalized in 

 mouth structure as well as in the way the 

 wings are carried. In this order the domi- 

 nance of the secondaries as organs of flight 

 is established, and the tegmina or primaries 

 are more and more changed in character. 

 The hind wings are always folded longitu- 

 dinally under the primaries and sometimes 

 both pairs are lost. In the primaries a 

 gradual change in position occurs, part of 

 the wing being first bent down in the crick- 

 ets to protect the sides, the character be- 

 coming more prominent in the Locustidss 

 and most obvious in the Acrididoe which, 

 in my opinion, are the highest of the order 

 in point of development. Some of the 

 roaches have the wings folded transversely 

 as well as longitudinally, and this is a very 

 primitive character which emphasizes the 

 relation of these insects to the Coleoptera 

 and points to a common ancestor. 



A prominent feature in the Dermoptera 

 and Coleoptera is that the secondaries are 

 transversely folded, separating these orders 

 at once from all the others except the few 

 roaches already mentioned . It is, of course, 

 true that there are Coleoptera in which the 

 secondaries are not transversely folded ; but 

 these are secondary peculiarities and ex- 

 ceptions to the rule. I am inclined to at- 

 tribute considerable importance to this 

 character, and to give these orders an inde- 

 pendent derivation from a Thysanuran 



