96 
Psyche 
[June 
The possible stages through which rotation evolved in the Blabe- 
roidea, from a polyphagid-like form is given in Fig. 25. The examples 
shown are not necessarily the ancestral lines. A species in which the 
ootheca possessed a long flange and was not rotated could have given 
rise, by reduction of the flange, to a blattellid-like species that did not 
rotate, or to a polyphagid-like stock that had a primitive type of 
rotation in which none of the eggs were held within the vestibulum. 
The polyphagids with primitive rotation could have evolved into 
advanced rotating individuals, by a complete loss of the flange, thus 
allowing the anterior eggs in the ootheca to remain in the vestibulum 
of the female. However, advanced rotation also could have arisen 
from a non-rotating blattellid whose ootheca lacked a flange and in 
which the anterior eggs were already housed in the vestibulum. 
Longer retention of the ootheca led to species like Blattella and finally 
retraction into the uterus occurred with the final evolution of ovovivi- 
parity, and viviparity in the Blaberidae. 
Since all of the Blaberidae that have been observed ovipositing are 
levorotatory (i.e., they rotate the ootheca so the keel faces the left), 
they probably arose from a Blattella- like stock that was levorotatory. 
Table 1 shows the direction of rotation of different species of Blat- 
tellinae. With the exception of Ectobius panzeri and Ischnoptera 
rufa rufa, the females of most species observed are dextrorotatory 
(i.e., they rotate the ootheca so the keel faces the right). Thirty 
percent of the oothecae of Ischnoptera rufa rufa were rotated to the 
left (Table 1). Individual oviposition records were kept of 15 
females of I. rufa rufa (Table 2), and it was found that 4 females 
were levorotatory, 4 were dextrorotatory, and 7 rotated in either 
direction. However, females that rotated their oothecae in both di- 
rections usually rotated predominately in one direction only (Table 2, 
females 5,7,8,10,11). 
Because the oothecae of Blattella spp. remain attached to the female 
during embryogenesis and the eggs gain water from the mother, this 
genus is considered to be an important link between the oviparous 
Blattellidae and the ovoviviparous and viviparous Blaberidae (Roth, 
1967). However, the 4 species of Blattella usually rotate their 
oothecae to the right (Table 1), whereas all the internal incubators 
(Blaberidae) are levorotatory. 
Brown (1952) suggested that Ectobius panzeri which generally 
rotates its ootheca to the left (Table 1) probably tends to rotate the 
egg case towards the side with the most eggs (if there is an odd 
number of eggs produced ) . I counted the eggs in 20 oothecae of 
Blattella germanica, all of which had been rotated to the right; in 
