216 THE entomologist's kecord. 



most frequent in islands and in mountains. Navas has suggested that 

 we may look upon it as a wild, savage race, and upon the commoner 

 cyclolabious form as a more or less domesticated race. 



In very many cases both forms are known, the cyclolabious being 

 as a rule the commoner ; such is the case in Labia ridens, Borm., and 

 many species of Forficida, but the macrolabious form seems to be a 

 little commoner in FAaunon hipartitus, Kirby. 



Only the cyclolabious form is known in several groups, as in many 

 Pt/f/idicranidae, Psalinae, Esphalmeninae, and others : only the macro- 

 labious form in AuchenoDnis lonf/iforcepfi, Karsch., S/ioni/iphora crocei- 

 pennis, Serv., Allodahlia, Forcipiila, Xesor/aster dolicliits, EiidoJirnia 

 metalUca, and many Ophhtocoamiinae. 



An exceptional ease is offered by Adiathetns sJtelfordi, Burr, in 

 which the male is only known in the cyclolabious form, and the 

 female in a highly developed macrolabious form ; only the macro- 

 labious form is known in both the sexes in Chelisochdla tiiiperba, Dohrn,. 

 and Adiathetus tenchrator, Kirby, Knkrates degans, Borm., and a few 

 other Chelisochidae. 



The difference in appearance between the two forms in Chelidnm 

 alpina, and Pseudochelidara sinuata, Germ., is ample excuse for the 

 former treatment of the two forms in each case as distinct spesies. 



Other forms of morphological variation occur in the forceps, which 

 are remarkable for their instability. 



The actual number and relative position of the teeth which often 

 form the armature of these organs is very variable, and numerous so- 

 called sub-species have been raised on the slender basis of the exact 

 position of the tooth ; thus in Spongiphora croceipennis, Serv., there is 

 usually a small tooth near the middle ; sometimes it is at the middle 

 itself, sometimes near the base, sometimes near the apex, sometimes it 

 is absent altogether : to this instability we owe the existence of the 

 names parallela, Westw., Ihenuinieri, Serv., and dysoni, Kirby, which 

 de Bormans ranked as subspecies ; similarly, Proreus sinnilans, Stal.,. 

 has a strong median tooth, but when this is absent it is the " sub- 

 species )iiodesta, Stal.," of de Bormans ; the same remark applies to 

 Nala livid i pes, Duf., and its " subspecies vicina, Luc." 



In those species in which the branches of the forceps are normally 

 bowed, or strongly arcuate, it is common enough to find specimens 

 feebly nourished and ill-developed, in which the curvature is far 

 weaker ; we get every degree from a very gentle curve to an abrupt 

 almost right-angled head, in Forticida scJdagintweiti, Burr, F. decipiens, 

 Gene, F. lurida, Fisch, and several Ancistrogastrinae, in which the 

 forceps have a well-marked group-form, with a strongly bent forceps. 



A rather curious variation occurs in the protean Labidura riparta, 

 Pall. Normally the males of this species have a pair of short spines or 

 points in the middle of the posterior margin of the last dorsal sclerite ; 

 these may be missing, as in the " var. incrmh, Br.," or there may be 

 only one present, and that in the middle, as in the form plnvialis, 

 Kirby. 



Pantel (1912) refers to the fluctuation in the number and appear- 

 ance of the chromosomes in Forficida anricularia, and quotes works 

 by de Sinety, Zweiger, Stevens, Carnoy and La Valette on the subject. 



II. Colour Variation. 

 The coloration of earwigs is very unstable. Frequently, the 



