Bibliographical Notice. 483 



the back of the female, but behind her ; and the position of the two 

 parties is such as if the male had originally been on her back, but had 

 fallen off on his own back. If one of them stands on the ground, the 

 other lies on its back ; the act can therefore only be performed be- 

 tween loose bark and the wood, or in other such localities, where they 

 can fix themselves in inverted position to opposite surfaces, blades of 

 grass, leaves, or other points of support. Dr. Meinert has several 

 times seen it performed, and always in such positions. He denies 

 that the forceps are used in copula for any purpose ; they are simply 

 laid along the respective ventral surfaces. He affirms that earwigs, 

 compelled by hunger, attack and devour one another. The number 

 of abdominal segments in Forficula has been very differently stated 

 by different authors, and is of importance with regard to the question 

 whether the abdominal segments in insect's exhibit a constant number 

 and homologic parallelism in their modifications, particularly in the 

 service of generation. Dr. Meinert maintains that the number is the 

 same in both sexes and in all stages of development — namely, nine be- 

 sides the segmentum mediale (Schj odte, = segment mediaire, Latreille), 

 which in the larvae is only represented by a dorsal shield, and which 

 Dr. Meinert considers to be the true first abdominal segment — a 

 necessary consequence of Prof. Schjbdte's discovery of the true stig- 

 mata mesothoracica in Hymenoptera *. The apparent sexual diffe- 

 rence of two abdominal segments less in the female than in the male, 



* The principal objection to Latreille's theory of the segment mediaire 

 was hitherto afforded by the position of the large spiracles at the back of the 

 thorax of Hymenoptera, which were always counted as the second pair. 

 But since Prof. Schjodte has discovered the true second pair in the same 

 place as in Coleoptera, behind the epimera mesothoracica, where they 

 are easily overlooked, as they are open only during the flight, this ob- 

 jection has been completely removed. The large spiracles in question 

 in the so-called metathorax of Hymenoptera evidently correspond to those 

 found in Coleoptera between metathorax and abdomen, and which Schjodte 

 prefers to callspiraculametathoracica(notabdominalial mi paris),because their 

 structure and size principally depends on the development of the organs of 

 the thorax, particularly of the elytra. According to Schjodte, the whole 

 matter stands thus : — The first abdominal segment developes itself differ- 

 ently from the neighbouring segments according to the following rule : — 



1 . The ventral shield is reduced in size in proportion as the third pair 

 of legs become more powerful, because the coxae, as they increase in size, 

 absorb a proportionate part of the space which otherwise would be occu- 

 pied by the first ventral shield. In some cases even a couple of the fol- 

 lowing segments are similarly reduced. 



2. The dorsal shield of the first segment of the abdomen (segment medi- 

 aire, Latreille ; segmentum mediale, Sch.) consequently alone remains, filling 

 up the space above the third pair of coxae, and necessarily conforming to the 

 hind part of the thorax in shape and size. Another necessary consequence of 

 the rudimentary state of the ventral shield of the true first segment of the 

 abdomen is this — that, in the case of an abdomen petiolatum, the petiolus is 

 formed by the second abdominal joint ; and the thinner the petiolus is 

 where it articulates on the first abdominal joint, the more must this first 

 segment (segmentum mediale) separate itself from the abdomen and unite 

 itself to the thorax. 



