70 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



THE ABDOMINAL APPENDAGES OF PROTURA 



A pair of short, cylindrical appendages is present on each of the 

 first three abdominal segments of all adult Protura. These appendages 

 arise from the membranous parts of these segments between the pos- 

 terior angles of the tergal and sternal plates. They are best developed 

 in Eosentomidae, where the three pairs are alike in size and structure, 

 and each organ (fig. 29 B) consists of two segments and a small 

 terminal vesicle (v) which is eversible and retractile. In Acerento- 

 midae (A) the appendages of the first pair are like those of the 

 Eosentomidae, but the second and third pairs are simple, tuberculiform 



Sex 



rv 



-Cx 



-Tlpd 



Fig. 29. — Abdominal appendages of Protura. 



A, Eoscntomon i/cnimnicum, abdominal leg (from Prell, 1913)- B. Accren- 

 tomon dodcroi, first abdominal leg (from Berlese, 1910). 



Cx, coxa ; /, promoter muscle of limb base ; /, remotor muscle : rv, retractor 

 of vesicle ; Sex, subcoxa ; Tlpd. rudiment of telopodite ; v, terminal vesicle. 



protuberances, unsegmented and lacking the terminal vesicle. Each 

 appendage of the larger type in the two families, as described by 

 Berlese (1910), is movable by two tergal muscles (B, /, /) inserted 

 on the basal segment, one anteriorly, the other posteriorly. The sec- 

 ond segment is provided likewise with two muscles, one arising 

 anteriorly, the other posteriorly in the proximal segment, the two 

 crossing each other axially to be inserted on opposite sides of the base 

 of the distal segment. The terminal vesicle is retracted by a single 

 large muscle (rv), which takes its origin mesally on the base of the 

 first segment of the appendage, and is inserted on a central depression 

 of the ventral face of the vesicle. The extrusion of the vesicle is 

 evidently brought about by blood pressure from within the body. 



