806 



ARTHROPODA 



PHYLUM VII 



primitive types of the suborder Symphyta were already in existence during the Mesozoic, 

 although the most primitive saw-flies (Lydidae or Pamphilidae) are not known from 

 rocks older than tlie Tertiary. About 2900 Recent species of saw-flies are known, 

 several are preserved in Baltic amber, and fifty or more have been described from 

 Tertiary strata in Europe and North America. Of this number thirty-three occur 

 exclusively in the Miocene lake beds of Florissant. Here belong 

 the genera Dineura and Taxonus Dahlb. ; Tenthredo Linn.; and 

 Atocus Scudder (Fig. 1558). A group of more highly specialised 

 Siricid-like Insects, constituting the extinct family Pseudo- 

 siricidae {Pseudosirex Weyenb.) (Fig. 1559) is rather abundant in 

 Jurassic formations of Eurojie, l>eing accompanied by forerunners 

 of the next higher suborder, Apocrita. A great expansion of 

 the order took place during tlie Cretaceous, contemporaneously 

 with the rise of Angiosperms. 



Nearly all of the principal modern families are represented 



in the Mid-Tertiary formations, as for instance true saw-flies of 



the family Tenthredinidae ; Siricidae ; various subfamilies of the 



parasitic Ichneumonidae ; small Cynipidae or gall-flies; Sphecidae; 



Vesjjidae or Avasps ; Formicidae or ants (Fig. 1560); and Apidae 



m'^rt ^'"'^*''^' ''^^ ^^^^^^ 01" bees. Ants are exceedingly abundant in the Miocene lake 



beds of Florissant, Colorado, thouvsands of individuals liaving been 



obtained, and true wasps and bees are also present in large numbers. About 



5000 species and sub-species of ants belonging to the modern fauna have been 



described, as compared with about only 300 Tertiary species. 



Fill. 15G0. 



P7-ion.omyrmex longipes 

 Mayr. Lower Oligocene; 



t Order 19. HADENTOMOIDBA Handlirsch. 



This order, comprising a single family and genus, is evidently derived from the 

 Palaeodictyoptera, and shows sjiecialisation in the reduced venation of the homonomous 

 wings. The small Carboniferous genus Hadentomum Handl. (Fig. 1561) is perliaps 

 transitional to the next following order. 



Order 20. EMBIOIDEA Kusnezow 



(Oligoneura Borner). 



Terrestrial Insects luith prognathous orthopteroid 

 mouth parts, homonomous free thoracic segments, 

 apterous or with homonomous wings showing re- 

 duced, venation. Antennae multiarticulate ; cerci 

 present ; first pair of legs with a spinning apparatus. 



Modern Embiidae are one of the smallest 

 families of Insects, not more than sixty species 

 being known from all parts of the world, and 

 the group being an obscure one. They are small 

 and feeble Insects, and, as indicated by their 

 wide distribution, are to be looked upon as the 

 remnants of a once flourishing stock. A few 

 fossil remains have been found in Baltic amber and 

 in the Miocene lake beds of Florissant, Colorado. 



Fic. 15()1. 



ITiulentomum amcricaniim Ilaniil. 

 Measures; Illinois. ^Yo (after Hand 



Coal 

 lirscli). 



