FAMILY II.— COCKROACHES. 89 



cases living young are produced, but none of our native 

 species have this habit. All young cockroaches resemble 

 their parents in form, but are wholly wingless, the wings 

 not appearing until after the fifth or last molt. 



To the paleontologist, interested in tracing back the an- 

 cestry of insects, the Blattidae are a group of surpassing in- 

 terest, as the oldest known insect is a cockroach described 

 from the Middle Silurian of France. About eighty fossil 

 species of this family are known. Prof. S. H. Scudder, our 

 eminent authority on fossil and recent orthoptera, says of 

 the cockroach: "Of no other type of insects can it be said 

 that it occurs at every horizon where insects have been 

 found in any numbers; in no group whatever can the 

 changes wrought by time be so carefully and completely 

 studied as here; none other has furnished more important 

 evidence concerning the phylogeny of insects." 



SYNOPSIS OF THE GENERA. 



Prof. Fernald gives the following synopsis: 

 Sub-anal styles wanting in the males; last joint of the 



abdomen of the female not divided Blatta. 



Sub-anal styles present in the males; last joint of the 



abdomen of the female divided 2 



(Supra-anal plate fissured Periplaneia.. 



\Supra-anal plate not fissured Platamodes. 



Prof. Scudder, in his "Guide to Or- 

 thoptera," has divided this order into 

 seven sub-families, two of which are 

 found in ourstate,the Blattinse contain- 

 ing the genera Ischnoptera {Platomodes) 

 and Blatta, and the Periplanetinae, 

 the genus Periplaneta. A number of un- 

 Fig. 52. — unwinged wingcd spccics of cockroachcs occur in 



Cockroach. Original. ^ ^. , - i i i , i 



Mmnesota under loose bark, but have 

 not been studied. Thc}^ are more or less active during 

 warm days in winter, and not easily captured even then. 

 One is shown in Fig. 52. 



