March, I9i6.] HebARD : GenUS StENOPELMATUS. 71 



plates show no other specialization and are in general similar, while 

 the structures within the anal orifice are soft, unmodified and in the 

 different species always become greatly shrivelled in drying. In the 

 females the supra-anal and subgenital plates show no specialization 

 and are likewise in general similar, while the ovipositor is very short, 

 simple, without teeth or roughened surface, and curved upward to the 

 sharp apex of the dorsal valves. 



Great dissimilarity in the sexes is shown in 5". longispina. With 

 little available material, the description of the male and female as 

 distinct species can be readily understood. This feature is shown to 

 a much less degree in the other species here considered. 



The spination of the caudal tibiae, a feature slight variations in 

 which have constituted the basis for descriptions of a number of 

 nominal species, shows decided variability in S. fuscus and 6". longi- 

 spina, though respectively different averages are found in the number 

 of spines and length of the distal spurs. Moreover, particularly in 

 longispina, sexual differences are found in the caudal tibiae. 



In all of the species here considered, as in the genotype, the teg- 

 mina and wings are absent. It is, partially due to this fact, exceed- 

 ingly difficult to separate adults from individuals in the last instars 

 preceding maturity. 



A megacephalic condition is developed in certain species, of those 

 before us much the strongest in 6^. fuscus, different individuals show- 

 ing this feature to varying degrees. In the maximum of this condi- 

 tion found in fuscus, more usually encountered in the male sex, the 

 head is enlarged out of all proportion to the body, this being particu- 

 larly pronounced in the occipital region (plate VII, fig. 2). The eyes 

 in such specimens sometimes differ in being decidedly protruding 



sequent stages to the adult condition, in all of which the subgenital plate is 

 fully developed, these hooks are likewise fully developed. In consequence, the 

 last stages of the immature condition, as is true also for the female sex, can 

 only be distinguished through familiarity with the adult condition, which may 

 be differentiated only through the more robust build and heavier structure 

 particularly of the head, pronotum and limbs. 



Brunner evidently compared an immature male of -S". talpa with an adult 

 male of 5. longispina, at the time he described the latter species. (1888. 

 Verh. zool.-bot. Gesellsch. Wien, XXXVIII, p. 260.) A male specimen of 

 S. talpa before us, from Mexico, shows the fully developed chitinous hook 

 exactly as in the species here studied. 



