334 FERNANDUS PAYNE 



The most striking difference between the chromosomes of Acholla 

 and Sinea is in the size relations of the idiochromosomes. In 

 Sinea all six of them are practically the same size while in Acholla 

 three of them are very small, two intermediate and one (the Y 

 element) very large. 



A study of the chromosomes of Pnirontis modesta Banks has 

 revealed a type of distribution new to the family and similar to 

 that described for Gelastocoris oculatus (Payne, '09). I have only 

 one specimen, but I believe it shows sufficient stages to justify 

 the above conclusion. Figure 2, A, B, and C show the spermato- 

 gonial group with twenty-five chromosomes, three of which are 

 very small. In the first spermatocyte division (fig. 2, D and E), 

 there are fifteen chromosomes. Again three of these are very 

 small. Of the remaining twelve, ten are larger and two inter- 

 mediate between the large and small ones. There is no definite 

 arrangement of the chromosomes and all divide in this division 

 so that all the secondary spermatocytes receive fifteen chromo- 

 somes. In the second division there is the characteristic regroup- 

 ing found in all the Reduviidae. The ten large chromosomes form 

 a more or less irregular ring with the two intermediate and three 

 small ones forming a pentad group in the middle. This group was 

 somewhat difficult to analyze on account of the small size of the 

 chromosomes and the fact that they lie so close together. Th^ 

 most favorable metaphases of the second division (fig. 2, F and 

 G) show, however, that four of these five, the three small and one 

 intermediate lie in one plane while the other intermediate one 

 lies below or above them. Figure 2, H, the best side view obtainable 

 of the second division, shows this one chromosome and its relative 

 position with respect to the other four, which in this figure are 

 massed together as one. Although no anaphases are present 

 showing the method of this division, I think there can be little 

 doubt, judging by the number relations in the spermatogonial 

 and first spermatocyte divisions and also from the analogy here 

 to the second spermatocyte divisions in the other Reduviidae, 

 that the ten chromosomes in the ring divide equally, while the 

 four members of the pentad group (X element), which lie in one 

 plane, pass to one pole undivided and the other one passes un- 



