244 THE ENTOMOLOGIST. 



seventy-three, ninety-six, or even one hundred and eleven of them. 

 "They were firmly fixed on the nervures towards, and at, the 

 base of the wing, and almost (but not quite) invariably on the 

 under side, and whatever might be the number on any particular 

 dragonfly it was always divided nearly symmetrically on the 

 two sides of the insect, those much infested having a very pretty 

 ai3pearance, from the wings appearing as if spotted with blood- 

 red " (Ent. Mo. Mag. xiii. p. 95, 1876). Two excellent plates ac- 

 company a paper by M. Krendovsky on the economy of the larvae of 

 Hydrachnidfe published in a Russian periodical (Trud. Charkov 

 Univ., 1878, Tom. xii, pp. 221-286). Figure 7 on Plate 1 shows 

 a specimen of S. meridionale having numerous mites, coloured 

 red, distributed in a remarkably symmetrical manner along the 

 principal nervures of the wings. Another figure (8) on the same 

 plate represents, again in colour, three of the mites on a large 

 scale. These mites are described as the six-legged larvae of 

 Arrhenurus papillator (Miill.), but, as will appear later, this 

 determination is by no means certain. 



Krendovsky also states that Hydrachnid larvae occur on the 

 sternum of S. flaveolum. This is the only case which has come 

 to our knowledge in which larvae have been found on the body 

 of an Anisopterid dragonfly. Some of the specimens of S. fons- 

 colomhii taken by Mr. C. A. Briggs in Surrey in 1892 were much 

 affected by a dark carmine-coloured Acarus; on one of the 

 dragonflies he counted as many as eighty-five parasites. Mr. 

 Briggs asks, "Do these Acari extract any colouring matter from 

 their host ? They exactly match the colouring of the nervures, 

 and one that I squeezed gave out a similar coloured fluid " 

 (Ent. Mo. Mag., ss. iii. p. 194, 1892). S. striolatum has also 

 been mentioned in this connection, but apparently in error for 

 S. meridionale. 



An example among the Gomphinae is afforded by a female of 

 Platygomphus dolahratus from India in the British Museum, 

 which has a red parasite on the left hind wing. 



But it is among the Agrioninae that Acari are met with most 

 abundantly, and our own collection furnishes examples of six 

 species which are infested to a greater or smaller extent. Those 

 species are Erythromma naias, Pyrrhosoina nymphida, Ischnura 

 elegans, Agrion pidchellum, A.jmclla, and Enallagma cyathigerum. 

 We have also noticed an immature female of P. tenellum in the 

 Stephens cabinet carrying a single mite on the sternum. 

 Furthermore, Krendovsky includes Lestes in the category of 

 mite-attacked dragonflies. In all the cases which have come 

 under our personal observation, the parasites are attached to the 

 under side of the thorax or abdomen, or both (but never to the 

 wings), sometimes in twos and threes, sometimes covering the 

 entire surface affected. In life they appear to the unaided eye 

 as globose bodies less than a millimetre in diameter when fully 



