40 BRITISH CICADA. 



In answer to my query Mr. A. Michael states — " It 

 is a fact, that all adult Acari are octopocl, except such 

 creatures as Fhytoptus, in which some of the legs are 

 abortive." 



On Plate XVII., fig. 3 b, of this Monograph will be 

 found a drawing of the brachypterous Liburnia limbata, 

 with two tick-like sacs attached, — one example is fixed 

 on one of the abdominal riugs, and the other on the hind 

 tibia. A microscopic examination of these scarlet-red 

 sacs proved them to be larvae of Trombidium fidiginosiim , 

 and that they were attached by certain claw-like pro- 

 cesses of the mouth, and perhaps aided in their hold 

 by two soft and fringed oral disks. The efficacy of 

 these claws is increased by the fact that each palpus 

 has its last joint articulate at the base. In Plate D, 

 figs. 10 and 11, I have figured this mite, but unfor- 

 tunately I have neglected to show in my enlarged 

 drawing this characteristic articulation of the palpus. 



This Acarus may be taken on such Cicadae as 

 Athysanus communis and Dcltocephalus oceUaris, and I 

 have found it fairly common also on some of the 

 Cecidomyidae, and on Phalangid^. Such sporadic 

 habits would seem to indicate that this mite is, in a 

 manner, indifferent to its local surroundings. 



Another species of Trombidium, T. holosericewn, like- 

 wise attaches itself to the bodies of some of the 

 Acocephalidae. It also has a bright red body, the head 

 is eyeless, and it has the projecting claw-like process 

 at the end of the palpus. The abdomen, however, 

 has more of a fiddle-like form than fidiginosum, and its 

 hard skin is furnished with many short scarlet hairs, 

 which make its integument appear somewhat silky. 



On the same plate (D, fig. 12) I have engraved an 

 Acarus of a cycloid form, with six legs, the species of 

 which is as yet undetermined. Its colour is yellowish, 

 with twelve roundish spots on the body-rings, disposed 

 in four rows of three each. This mite infests several 

 species of Libimiia, and, like other larv« of this group, 

 it possesses only six legs. 



