ENEMIES OF APHIDES. 375 



II. — Fore part of head not ])rolonged into a distinct 

 beak. 



A. — Skin firm. 



1. Skin scarcely extensible, palpi not seated on 

 a common chin piece. 



(a) Chelicerffi, claw or needle like; Palpi 

 terminated by pair nippers ... Trombidiidce 

 Palpi, with bristles or hook at end ... HydracJmidce 



(b) Chelicerae, with nippers ; first joint of 



Palpi very large ... ... OribatidcE 



Joints of Palpi nearly equal ... Cramasidce 



2. Skin leathery, very extensible \ Palpi attach- 

 ed to a chin plate ... ... ... Ixodidce 



B. — Skin soft, with few chitinous bands ... ... Acaridce 



EXPLANATION OF PLATE XVII. 



Fig. 1. — Acarus (species ?) attacking Aphis on apple leaf (from a 

 mounted specimen shewing both in natural positions). 



,, 2. — Larva of a Trombidium, with Poppy Aphis on leaf. This 

 larva was apparently parasitic of the aphis. 



,, 3. — Leg of larva in last figure. 



,, 4. — Palpi and mouth parts of Trombidium holosericeuni. 



,, 5. — Leg and claw of last. 



,, 6. — Acarus (species?), taken by Mr. Watkins, attacking Aphides. 



,, 7. — Claw of last. 



,, 8. — Eggs and web (after Miss Omerod). 



,, 9. — Tetranychn^ telarius, Linn, (after Miss Omerod). 



According to Meehan's Afonthly, the large majority of plants 

 are scentless, and probably not one-tenth of the hundred thousand 

 flowering plants known to botanists are odorous. Of the fifty 

 known species of the mignonette family, only the one so highly 

 prized in our gardens is fragrant, and only about a dozen of the 

 one hundred species of violet are scented. In many large genera 

 the scentless varieties are as one hundred to one, and sweet-smell- 

 ing varieties are comparatively rare among our wild flowers. 



