808 



ARTHROPODA 



PHYLUM VII 



Order 23. PERLARIA Handlirsch {Plecoptera Burmeistei). 



Amphibious Insects unth prognathotis orthopieroid mouth parts and long multi- 

 articulate antennae. Body segments very nearly homonomous, legs fairly similar, and 



wings with a rather specialised venation, generally shoioing 



^„^s» ^'^^^'''^^^S!^^^^ ^:^,i^ ^^,^^ a few cross-veins. Hind wings often with a conspicuous 



folded anal lobe ; cerci usually well-developed ; tarsi three- 

 jointed ; females toithout a prominent terebra. 



Fid. 1564. From tlie Permian of Russia and North America 



Leiictm gracilis Pictet. Lower are known a number of Insect remains wliicli appear to 

 OliETOcene ; Baltic amber, ••/i (after ^ ^ ^ J_^ • j i ^ i • i j. • 



Pictet). belong to this order, but whose precise relations are 



difficult to determine. A few undoulited representatives 



of the order, such as Mesonemura, Mesoleucfra and Platyperla Brauer, occur in the 



Middle Jura of Siberia, and several genera, including Perla Geoffr., and Leuctra 



Steph. (Fig. 1564) are preserved in Baltic amber. 



t Order 24. PROTEPHEMEROIDBA Handlirsch. 



Amphibious Insects of Palaeodictyopteran aspect. JVings homonomous, with a very 

 primitive venation and numerous cross-veins, but also showing intercalary veins extending 

 longitudinally. Thorax and abdomen, with very 

 nearly homonomous segments ; legs similar ; cerci 

 long. 



Here is j)laced the solitary genus Triplosoba 

 Handl. { = Blanchardia Broiign.) (Fig. 1565) from 

 the Upper Coal Measures (Stephanian) of Com- 

 mentry, France. It is regarded as a connecting 

 link between the Palaeodictyoptera and true 

 Ephemeridae or may-flies belonging to the next 

 order. 



Order 25. PLECTOPTERA Packard 



{Agnatha auct.). (May-Hies). 



Fio. 1565. 



Triplosoha ind chcU a (BroDgn.). Stephan- 

 ian ; Comnientry, France. Vi Oifter 

 , ., , . . Brongniart). 



Delicate amphibious Insects with atrophied ortho- 

 pteroid mouth parts, short antennae, and four membranous wings having both intercalary 

 and cross-veining ; the hinder pair in all Recent and many fossil 

 species more or less reduced and sometimes wanting. Antennae 

 short, with two basal joints and an apical needle-like segment. 

 Ocular organs large, often divided. Prothorax small, legs slender, 

 the first 2yair elongated, antenniform ; tarsi more or less reduced ; 

 cerci slender, very elongate; last segment often filiform. Larvae 

 loith respiratory abdominal legs. 



This order is well represented in the Permian, Jurassic, 



and Tertiary deposits of Europe and North America. The 



older forms differ from existing Ephemerids in having the hind 



Fir, 15G6 wings equal in size to tlie front pair, and in having more com- 



Cronicus anomalus pHcated venation. Later and more highly specialised forms 



(Pictet). Lower oiigo- have reduced venation. Nearly 300 species of may -flies are 



cene ; Baltic amber, 

 (after Pictet) 



^/a 



known in the modern fauna, but these probably represent, as 



