Stapliylinida of the Amazon Valley. 79 



above described is one of the largest and most developed 

 males ; the thorax is sometimes infuscate, and even quite 

 pitchy, and the dark colour in other cases reduces the pale 

 colours to smaller areas. The tubercles on the elytra of 

 the male seem in some cases nearly to disappear, and pos- 

 sibly in some individuals of that sex may be quite absent. 



11. GyrophcEna debilis, n. sp. Rufo-testacea, nitida, 

 parcissime punctulata, capite, elytris apicem versus, ab- 

 domineque ante apicem infuscatis ; oculis maximis. Long. 

 Corp. I lin. 



The male of this species has a minute tubercle at the 

 hinder and inner angle of each elytron ; the dorsal plate 

 of the 6th segment of the hind body has an indistinct 

 impression on the middle of the basal portion ; the hind 

 margin of the foUoAving plate is narrow, and very nearly 

 truncate ; the middle being scarcely visibly prominent, 

 and the outer angle on each side bearing only a very short, 

 indistinct, obtuse projection. 



Rio Purus, 13th October, 1874 ; a single male found 

 by Dr. Trail, and a second individual found at Garrao, in 

 fungus, on the 11th November, 1874. 



Ohs. — I am by no means sure that this individual may 

 not ultimately be shown to be an extremely undeveloped 

 male of the variable G. hoops. It is, however, rather 

 smaller than the smallest individual of that species, and 

 the colours are paler than the palest thereof; the 4tli joint 

 of the antennae appears to be smaller in proportion to the 

 5th, and the male peculiarities of the hind margin of the 

 7th segment are so reduced as to be almost absent. Should 

 this insect ultimately be shown by a series of intermediate 

 individuals to be a mere form of the G. hoops, we shall 

 then have demonstrated to us that the male secondary 

 sexual characteristic in this species (as is known to be the 

 case with many larger Coleoptera of different families) 

 may be in some individuals almost entirely absent ; and 

 this will be all the more interesting, as in this case we shall 

 see that this diminution of the male peculianties extends 

 even to those external parts that are in most immediate 

 proximity to the primary sexual organs ; for I have con- 

 vinced myself, by numerous dissections of Gyrophcence, 

 that the cedeagus and its coverings have their chief attach- 

 ment to the dorsal plate of the 7 th segment of the hind 

 body. 



