HOW TO KNOW THE IMMATURE INSECTS 



2a. Abdominal terga each with one or three transverse sutures. 



Fig. Ill Family ACERENTOMIDAE 



The proturans are minute whitish organisms. The 

 largest species scarcely attain 2 mm. in length. They 

 are widely distributed in Europe, Asia and America. 



Fig. in. Aeeren- 

 tomon doderoi 



Silvestri. 



2b. Abdominal terga without transverse sutures. 



Fig. 112 Family PROTENTOMIDAE 



Proturans are peculiar in that they walk only on the 

 middle and hind legs and hold the fore legs in front 

 and above the head. 



Pig. 112. Micro- 

 entomon perpo- 

 sillom. 



ORDER THYSANURA 



la. 3 caudal appendages; compound eyes present (Suborder Ectotro- 

 phi). (See Figs. 113 and 114) 2 



lb. 2 caudal appendages; compound eyes absent (Suborder Endotro- 

 phi). (See Figs. 115 - 118) 3 



55 



