332 FEKNANDUS PAYNE 



rileyi, which presents a type of distribution similar to that of 

 Acholla multispinosa, might lead us to the opposite conclusion. 

 If there were present in the parent species a type of distribution 

 similar to that of Sinea diadema we would have to assume a fur- 

 . ther splitting up of these chromosomes in order to reach the con- 

 dition found in Sinea rileyi. Such an assumption would only 

 complicate matters. In this case it would seem that this species 

 split off from the parent one before any breaking up of the single 

 large idiochromosome had occurred, assuming, of course, that 

 a single pair of idiochromosomes was the original condition. In 

 all probability then, the breaking up of the large idiochromosome 

 has occurred independently in the parent species and in Sinea 

 rileyi and, of course, may have occurred at any time since the 

 origin of the species. 



As the type of chromosome distribution found in Sinea rileyi 

 has been described in only one other species it seems worth while 

 to describe it somewhat in detail. Unfortunately, I have a 

 small amount of material and it does not show spermatogonial 

 or oogonial divisions. However, first and second spermatocyte 

 divisions are in abundance and, I think, indicate clearly that the 

 type of distribution is similar to that of Acholla multispinosa 

 (Payne, '09 and '10). The first spermatocyte division (fig. 1, 

 A and B) shows eighteen chromosomes, six of which are smaller 

 than the remaining twelve. All divide in this division so that 

 each secondary spermatocyte receives eighteen chromosomes. 

 There is no definite arrangement of the chromosomes in the first 

 division but the characteristic regrouping, found in the remainder 

 of the Reduviidae, occurs in the second division. The twelve 

 larger chromosomes are arranged in an irregular ring with the 

 six smaller ones forming a hexad group in the middle. Five of 

 these six lie in one plane while the other one lies in a different 

 plane either above or below the five. Figure 1, D and E are pole 

 views of this division showing the twelve chromosomes in the 

 ring and the five which lie in one plane in the middle. Figure 1, F 

 is the same as E, but drawn at a different focus to show the one 

 chromosome in the middle instead of the five. Figure 1, (? is a 

 slightly oblique view showing the hexad group. Figure 1, H is a. 



