808 



ARTHROPODA 



PHYLUM VII 



Order 23. PBRLARIA Handlirsch {Flecoptera Burmeister). 



Amphibioiis Inseds with procjnathous ortJiopteroid mouth parts and long multi- 

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

 wings with a rather specialised venation, generally showing 

 a few cross-veins. Hind wings often with a conspicuons 

 foldedanal lohe; cerci usually well-developed ; tarsi three- 

 jointed ; fem,ales without a prominent terehra. 



Fi.i, 1564. From tlie Permian of Russia and North America" 



l^idra gracilis Pictet. Lower are known a number of Insect remains wliicli appear to 

 PiSr^'^''^*'''^'"^''" '^^ ^'''^^''" l^eloiig to this Order, but whose precise relations are 

 difficult to determine. A few undoubted representatives 

 of tlie Order, such as Mesonemura, Mesoleuctra and Platyperla Brauer, occur in the 

 Middle Jura of Siberia, and several genera, including Perla Geoft'r., and Leuctra 

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



t Order 24. PROTEPHBMEROIDEA Handlirsch. 



Ämphibious Inseds of Palaeodidyopteran asped. Wings homonomous, with a very 

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

 longitudinally. Thorax and ahdomen with very 

 nearly homonomous segments; legs similar; cerci 

 long. 



Here is placed the solitary genus Triplosoha 

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

 the Upper Goal 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-flies). 



Delicate ämphibious 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 pair 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 

 wings equal in size to the front pair, and in having more com- 

 (Pictot) fower"or"" }^^^^*^^ /^'^^a^ion. Later and more highly specialised forms 

 cene -Baltic amber. '^3°; [^^^^ leduced venation. Nearly 300 species of may-flies are 

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



Fig. 1565. 



Triplosoha pulchella (Brongn.). Stephan- 

 ian ; Commentry, France. Vi (after 

 Brongniart). 



Fio, 1566. 

 Cronicus anomalus 



(after Pictet). 



