NOTES ON DRAGONFLY PARASITES. ^\k^^ 243 



legs. All known species of Acari belonging to the genus 

 Ca7iestrinia, Berlese, are found upon insects, and mostly upon 

 Coleoptera ; numerous Gamasidae, when in the immature stages, 

 are found wholly or chiefly upon Coleoptera. Prof. C. V. Kiley 

 has published an interesting account ('American Naturalist,' 

 xii. p. 139, 1878) of his researches into the life-history of the 

 North American locust-mite, to which he gives the name Trom- 

 hidium locustannn. Speaking of the newly-hatched larvae, he 

 says : " These little six-legged specks crawl upon the locusts and 

 fasten to them, mostly at the base of the wings or along their 

 principal veins." He adds : " That they are often so numerous 

 as to weaken and kill their victim, reports clearly prove." Most 

 aquatic Khynchota are subject to the attacks of water-mites, and 

 Prof. Eiley says that over five hundred have sometimes been 

 counted on a single specimen of' Zaitha (Belostoma) fluminea, 

 Say, a large American species. Coming to the Neuroptera, we 

 may cite a female scorpionfly {Panorpa gennanica) taken by 

 ourselves in Epping Forest, and having a mite located on the 

 under side of the right hind wing. 



It must, however, always be remembered that the word 

 " parasitic " is used in different senses by various writers, and 

 that the meaning of the word as used by most biologists is wider 

 in its signification than that attached to it by the popular idea. 

 It is necessary to remember this when dealing with the Acari, 

 as so many of that group of creatures, particularly in the imma- 

 ture stages, seek only conveyance from the host on which they 

 are found, and not nourishment ; the parasitism being temporary 

 and apparently for the purpose of the distribution of the species 

 of mites : this is chiefly confined to terrestrial Acari, as far as is 

 at present known. There are numerous other variations in the 

 nature of the relations of the so-called Acarine parasite to the 

 host upon which it is found. 



Although water-mites attach themselves so freely to many 

 kinds of aquatic insects, we have not yet met with any instance of 

 a nymphal dragonfly being attacked by them. We are acquainted 

 with eases in which Acari have attacked imaginal dragonflies 

 belonging to the sub-families Libellulinse, Gomphinte, and 

 Agrioninae. Among the Libellulinae, Sympetrum meridionale is 

 a notorious instance: indeed, McLachlan wrote of it that "its 

 liability to have the well-known red Acari attached to the wings 

 (sometimes in enormous numbers) is so marked as to be almost 

 a specific character of the insect itself, few specimens being en- 

 tirely free from them " (Ent. Mo. Mag. xx. p. 253, 1884). Thir- 

 teen examples of this species taken casually in France were ex- 

 hibited by Mr. McLachlan at a meeting of the Entomological 

 Society of London. Only one of them had escaped attack, but the 

 remaining twelve carried between them no fewer than four hun- 

 dred and eighty-one parasites. Single specimens had as many as 



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