1920] Ewing: Genus Trombicula Berlese 389 



or burrow into the sand provided for it in the breeding vial. 

 Individuals thrive only with a very moist atmosphere, even 

 saturation is not injurious to them. Their coats of feathery 

 setas keep their bodies dry. When placed in water they come 

 rapidly to the top and can walk about over the surface. 



In order to enable dijfferent workers to determine species of 

 the genus and in order to call attention to certain characters 

 which alone are of value in separating the different species, a 

 key to all those known up to the present is here given. 



KEY TO THE SPECIES OF THE GENUS TROMBICULA BERLESE. 



A. Eyes present and well developed; setas of body but slightly longer on the 

 posterior margin than on the shoulders, and colored. 

 B. Palpus armed with four spines on the inner side of tibia; adults about 



L5 mm. in length T. minor Berlese 



BB. Palpus armed with only three spines on the inner side of tibia; adults 



not over 1.0 mm. in length T. cinnabaris n. sp. 



AA. Eyes vestigial or absent; setae of body considerably longer on the 



posterior margin than on the shoulders. 



B. Anterior tarsi much less the three times as long as broad; palpus 



armed with four accessory spines. 



C. Posterior lobes of pseudostigmatic area larger, rounded and not 



behind the pseudostigmata; pseudostigmatic hairs arising inside 



of pseudostigmata; body hairs thinner at their tips than elsewhere, 



T. splendens Ewing 

 CC. Posterior lobes of pseudostigmatic area smaller, more or less angu- 

 late and immediate^ behind the pseudostigmata; pseudostigmatic 

 hairs arising from the bottoms of pseudostigmata; body hairs not 



thinner at their tips T. coarctata Berlese 



BB. Anterior tarsi much more than three times as long as broad; palpus 

 armed with three accessory spines. 

 C. Total length much more than 1.5 mm.; anterior tarsus over four 



times as long as broad T. formicarum Berlese 



CC. Total length less than 1.5 mm.; anterior tarsus considerably less 



than four times as long as broad T. canestrinii BufTa 



SYNONYMY. 



The suggestion of the synonymy of T. mediocris with T. 

 minor is received with some hesitancy, and as here given is 

 based upon the study of the nymphal characters of the "kedani" 

 by various Japanese workers. More data is needed in regard 

 to the life history of minor before the question of synonymy 

 can be settled with certainty. 



Trombicula minor Berlese. 

 1905. Trombicula minor Berlese. Acari Nuovi. Redia, Vol. II, pp. 155-156, 



Tav. XV, Figs. 4 and 4a. 

 1912. Trombicula mediocris Berlese. Troml^idiidae. Redia, Vol. VIII, pp. 93-94. 



Fig. 43. 

 1912. Trombicula minor Berlese. Trombidiids. Redia, Vol. VIII, pp. 94-95, 



Fig. 44. 

 1918. Trombicula mediocris Berlese. Kitashima and Miyajima: Studien Ueber 



die Tsutsugamuslii-krankheit. Kitasato Archiv. Exp. Med., Vol. II, 



pp. 190-191, Taf. VIII, Fig. 2. 



