138 ARACHNOIDEA. 



CASE down the numbers of the locusts, may be its further stage, and it 

 would be curious if it were so ; then it would be the young mite 

 attacking the old locusts, and the old mite attacking them in their 

 youngest stage : viz., in the Qgg. Seeing how little mischief the 

 larvae of Tr. holosericeum seem to do to the Phalangium, on 

 which they fix themselves, it was scarcely to be expected at first 

 sight that they would have any great effect in diminishing the 

 number of the locusts ; but it appears to be otherwise. Mr. Riley 

 quotes various informants who speak to their destroying them in 

 perceptible numbers ; and one paper. The Prairie Farmer, which 

 has acquired renown for its accurate entomological news, says 

 (August 21, 1869), ''the course of the locusts was brought to a 

 sudden halt here by the operation of some parasites, appearing in 

 the shape of small red mites, which attach themselves to the body 

 under the wings, where they suck the carcass to a dry shell ; the 

 dead bodies of the grasshoppers almost covering some plants, 

 where they have taken hold of a leaf or a stalk, and clasped it 

 with a dead embrace ; many others fall to the ground, too weak 

 to rise again. In a half-day's examination, where they were very 

 thick, we failed to find more than two grasshoppers not so attacked, 

 and this was not local, for a distance of thirty 

 miles across the country they were found 

 similarly affected." 



Trombidium sericeum (^Vzy). — 23, Magnified sketch 

 of ditto, copied from Mr. Riley's Seventh Missouri 

 Report. 



Only two species of North American Trom- 

 bidium having been hitherto described by 

 Say, and these only in brief terms, it is very 

 possible that this is a new species; but Mr. 

 Riley has wisely declined (although not without hesitation) to 

 run the risk of adding to the synonymy — and as he has given a 

 good figure of it, this will in future be the type of Say's imperfectly 



Trombidium sericeum. 



