42 PREDACIOUS AND PARASITIC ENEMIES OF APHIDES. 



section, together with the organs of generation, and observations 

 upon the food found in the viscera of some species. 



5> 



EXPLA.NATION OF PLATES III. & IV. 



Plate III. 



Fig. 1. — Details of anterior segments of larva of S. luniger. a, 

 Piercing organ. 6, Pharynx, c, Palpi, d, cZ, d, Muscles 

 controlling the movements of mouth parts, e, Mass of mus- 

 cular fibres surrounding pharynx. f, One of the hooks. 

 , • g, g. The anterior inlets of the main tracheal trunks, h, h. 

 i, The nervous centre, consisting of many combined 

 ganglia, and giving off numerous nerve-threads (k, k) to the 

 different segments. I, Tracheal loops to provide for circula- 

 tion of air during the invagination of mouth parts, m. Cross 

 tracheae connecting main trunks with tracheae of nerve centres. 

 These are duplicated, n, Salivary glands, o, (Esophagus. 



,, 2. — Chitinous portions of piercing organ. 

 3. — Points of same, enlarged. 



4. — Muscle surrounding same, the pharynx being shown by 

 dotted lines. 



,, 5. — View of sucking organ, with blades opened. 

 ,, 6. — Point of piercing blade, much enlarged. 



,, 7 and 8. — Posterior terminations of tracheal trunks, showing 

 structure of chitinous valves. 



,, 9. — Under view of front parts of larva partially evaginated. 

 a, a, 6, h, The frontal palpi with their papillae, c, c. d, The 

 cleft of the mouth, e. The extremity of the piercing organ, 

 just visible. /, Pair of palpus-like organs on the borders of 

 the mouth, g, Border of mouth, h, h, Chitinous hooks. 



Plate IV. 



Fig. 1. — Alimentary system of Syrphidcb as illustrated by Eridalis 

 tenax. 



d, b, c. The three joints of the proboscis, d, Tongue, 

 e, Labium. /, /, Maxillae, g, Labial palpi, /i, Pharynx. 

 i, CEsophagus. k, Passage to crop, k', Crop empty of food 

 and collapsed ; a few grains of pollen are visible within. 

 I, Stomach, m, Proventriculus or gizzard. n, ?</, Secretory 

 organs delivering gastric or other digestive fluids to the pro- 

 ventriculus. 0, o, Salivary glands, which have their ultimate 

 outlet in the tongue. It has been impossible to trace the 

 ducts throughout, p, p, Intestines distended with food. 

 q, q, Hepatic vessels discharging into lower end of intestines, 

 r, r, Lower intestines, v, v. Rectum, s, Enlargement of 

 rectum containing the renal organs, t, t. u, u, Traclieal 

 vessels supplying air to renal organs. 



2.— Proboscis of Syrplms luniger, with lobes extended and viewed 

 obliquely. The same lettering applies as to Fig. 1. 



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