18 



epiphallus. The ventral phallomere (= vla-lobe in the previous description) Hes ventral to 

 the genital opening (in a strict morphological sense anterior to it); i.e. the genital opening 

 is in its anteriormost dorsal wall. The right phallomere (= right phallomere in the previous 

 description) and the left phallomere (= left complex minus the vla-lobe) have their bases 

 in the areas dorsal (in a strict sense: posterior) and lateral to the genital opening. Snodgrass 

 (1937) deduces this basic division from his investigations of the ontogenetic stages of the 

 phallomere complex in Periplaneta americana and Blatta orientalis (both: Blattinae): In 

 medium-sized nymphs the phallomere complex consists of three distinct lobes, which 

 hardly reveal any further elaborations. One lobe is situated medioventral to the prospective 

 genital opening (prospective ventral phallomere), the other two take positions dorsolateral 

 to the genital opening (prospective right and left phallomeres). Thus, a composition of a 

 medioventral, a right-dorsal, and a left-dorsal basic element seems plausible, and according 

 to Snodgrass (1937) the ventral phallomere is an unpaired medio ventral element. 

 Quadri (1940) studied the ontogeny of the phallomere complex of Blatta orientalis in more 

 detail. In first instar nymphs he finds one pair of lobes with an invagination between them 

 (rudiment of ejaculatory duct). In the third instar each lobe is divided into a dorsal and a 

 ventral secondary lobe, and thus four lobes surround the prospective genital opening. Later, 

 the two left lobes form the left phallomere (more or less by fusion, without any clear 

 border remaining). The ventral right lobe shifts to the left, into a position beneath the 

 genital opening, and becomes the ventral phallomere. The dorsal right lobe maintains its 

 position and becomes the right phallomere. Thus, according to Quadri, the ventral 

 phallomere is a ventral part of the right half of the phallomere complex. Later Snodgrass 

 (1957) took over the opinion of Quadri but still used the tripartite division in his 

 terminology. 



Concerning the assignment of the ventral phallomere, or ventral lobe via, my own 

 observations as well as the mode of innervation (Pipa 1988) are in conflict with the views 

 of both Snodgrass (1937) and Quadri (1940): 



In some aberrant specimens of Blattaria the phallomere complex is completely 

 symmetrical. I could find two such specimens: (1) Polyphaga aegyptiaca (Polyphaginae) 

 with two "right" phallomeres being mirror-images of each other; there was no trace of a 

 ventral phallomere, which is present in normal specimens. Unfortunately, the specimen 

 had been dried and macerated, and the relations to the internal genitalia and the presence 

 of an ejaculatory duct could not be investigated. (2) Deropeltis sp. (Blattinae) with two 

 "left" phallomeres and two complete ventral phallomeres, both pairs being mirror-images 

 of each other. The phallomere-gland is paired. The ejaculatory duct is, as usual, unpaired. 

 It opens in the median plane - in that area where the dorsal walls of the left and the right 

 ventral phallomeres are confluent with each other. Thus, the location of the genital opening 

 - in relation to the ventral phallomeres - is the same as in normal specimens, and the two 

 ventral phallomeres are arranged in a way that this relative position is true of both of 

 them. 



Pipa (1988) studied the innervation of the male postabdomen in Periplaneta americana: 

 From the posterior part of the last abdominal ganglion - a compound ganghon formed 

 from the ganglion rudiments of abdominal segments 7 to 1 1 - one pair of nerves runs to 



