70 



Wiss. Wien, 1859, p. 189 describing Pimelonyssus trichorion Klti. 

 he says: »in der Richtung der stark hervortretenden Stigmen- 



wulste " etc. And yet, the length and the direction' of the 



peritrema and the situation of the stigma in Spinturnicinae may 

 be a good characteristic. 



In no case can the direction of the hairs be a characteristic, 

 as it is too often considered to be by Kolenati. This direction 

 is very variable in the same species; it all depends on the amount 

 of food, if not on other circumstances. 



In no case can the situation of the stigma on the dorsal or ventral 

 side always be a specific characteristic, as in fact it is ventral (in 

 most species) in nymphae and females, dorsal in males; but when 

 the nymphae and females are fasting, the stigma becomes quite 

 lateral, nay even often dorsal. And when the stigma is in fact 

 ventral, the observer is usually mistaken owing to the extraordinary 

 transparency of the skin, so that with low powers the stigma 

 always seems to be dorsal ! 



Erosionsgruben (Kolenati !) are pits or groups of small pits, 

 which in living or dried, specimens are distincty visible through 

 a pocket magnifying glass, when the animal is viewed a little 

 obliquely. The general arrangement of these pits may be a very 

 good characteristic for distinguishing species, but in no case can the 

 number be used for this purpose, as Kolenati has too often done. 



There are no hexapod larvae, but the newly born octopod mite 

 is a nympha, provided with stigmata and peritremata ! By authors 

 on Acari in general, or on Parasitidae in general, or on Spinturni- 

 cinae in particular this nympha is always called a larva! As is 

 well known, larvae are provided with 6 legs and have no 

 tracheae! This phenomenon must be explained by the parasitism 

 on flying mammals. Nymphae are stronger than larvae and more 

 adopted to its manner of living. The phenomenon is similar to 

 that of Pinnipeds, in which the newly born pups have their 

 permanent dentition at once, whilst the deciduous dentition is 

 rudimentary, never truly functional, and generally not persistent 

 beyond the foetal stage of the animal. 



