NO. 8 INSECT ABDOMEN SNODGRASS 4I 



more extensive comparative study of the ovipositor, however, Cramp- 

 ton (1929) repeatedly confused the valvifer and the basivalvula be- 

 cause he did not base his identifications of these sclerites on their 

 relations to the rest of the mechanism of the ovipositor. His *' val- 

 vifer " in Gryllohlatta, Centhophilus, Gryllus, and Hymenoptera, for 

 example, is the sclerite he calls " basivalvula " in Hemiptera, while in 

 Periplaneia he gives the name " valvifer " to a sclerite that belongs 

 to the ninth tergum. The sclerite designated first valvifer in the present 

 paper, therefore, is the " valvifer " of Crampton as he applied the 

 term in Grylloblattidae, Tettigoniidae, Gryllidae, and Hymenoptera, 

 and the homologous sclerite in other insects as determined by its 

 muscle attachments and its relation to the first valvula. In his hypo- 

 thetical diagrams Crampton (1929, figs. 1-4) derives the valvifer from 

 the ninth tergum, probably because the sclerite he calls " valvifer " in 

 Blattidae is a part of the ninth tergum, but he gives it no connection 

 with the first valvula, though this is its most distinguishing and char- 

 acteristic feature in the mechanism of the adult ovipositor in all insects. 

 Crampton's diagrams, however, do not represent actual anatomical 

 conditions, and it is only by a detailed dissection of the parts in ques- 

 tion that the true identities of the A^arious basal elements of the ovi- 

 positor can be determined. 



Since the term valvifer is a very appropriate one when consistently 

 used, inasmuch as it signifies literally a sclerite supporting a valvula, 

 the writer here introduces the innovation of extending it to both pairs 

 of valvula-bearing plates, distinguishing those that carry the first 

 valvulae as the first valvifers, and those that carry the second and third 

 valvulae as the second valvifers (usually called " coxites " of the ninth 

 segment). The term basivalvula fittingly signifies the small sclerites 

 that sometimes occur at the bases of the first valvulae, so named by 

 Crampton (1917, 1929) in Gryllohlatta, Tettigoniidae, and Gryllidae. 



The leading facts in the ontogenetic development of the ovipositor 

 are too well known to be given here more than a brief review. All 

 investigators agree that a pair of processes grow out from the under 

 surface of the eighth abdominal segment, and a second pair from the 

 under surface of the ninth segment, and that each of the processes of 

 the second pair typically becomes double by dividing lengthwise, or by 

 budding an inner lobe from its mesal surface. The processes of the 

 eighth segment in most cases become the first valvulae; the outer 

 processes of the ninth segment form the second valvifers, including 

 the terminal lobes of the latter, while the inner processes become the 

 second valvulae. It is claimed by Nel (1930) that the definitive first 

 valvulae of Odonata and Orthoptera are not the gonapophyses of the 



