ON THE BRITISH SPECIES OF SIMULIUM — II. 223 



9. Cocoon with a long anterior projection ; upper pair of filaments with a long 

 vertical stalk ; lower filaments twice dichotomously branched from base 



subexcisum, Edw. 

 Cocoon without anterior dorsal projection ; filaments otherwise . . . . 10. 



10. Filaments all widely divergent at the base, the uppermost one nearly vertical 



for a short distance . . . . . . . . argyreatum, Mg. 



Filaments not widely divergent at base, all more or less in the same vertical 

 plane, arranged in three shortly stalked pairs . . . . . . 11. 



1 1 . Filaments somewhat divergent, all about the same thickness ; cocoon aU closely 



woven, as long as the pupa . . . . . . . . venustum, Say. 



Filaments scarcely divergent, the lower pair somewhat thinner than the upper 



12. 



12. Cocoon short, usually not extending beyond the middle of the thorax ; filaments 



longer than the pupa, directed straight forwards . . tuberosum, Ldst. 



Cocoon longer than the pupa ; filaments shorter . . . . . . . . 13. 



13. Cocoon all closely woven ; upper pair of filaments considerably thicker than 



the lower . . . . . . . . . . . . monticola, Fried. 



Cocoon loosely woven at the sides in front ; upper pair of filaments not quite 

 so stout . . . . . . . . . . . . . . variegatum, Mg. 



14. Filaments in two distinctly stalked pairs ; cocoon with anterior projection 



latipes, Mg. 

 Filaments aU arising from a common base, or nearly so . . . . . . 15. 



15. Filaments very stout at the base ; cocoon with anterior projection (short or 



long) . . . . . . . . , . . . . angustitarsis, Ldst. 



Filaments slender at the base ; cocoon without anterior projection 



aureum, Fries. 



1. S. ornatum, Mg. (figs, la, 2a, 3a, ia db). 



Larva. — General colour variable, usually greenish grey or dingy greenish -yellow, 

 without special markings on the body. Head light yellowish-brown ; a median 

 wedge-shaped dark mark near posterior margin of clypeus ; a spot on each side of this 

 and sometimes a trace of a fourth anterior to the wedge-shaped mark ; usually also 

 pairs of marks on each side at the posterior margin ; a dark stripe above and in front 

 of the eyes. Antennae 5- jointed ; first joint usually a little shorter than second, which 

 is often very imperfectly separated from the first and sometimes obscurely divided 

 into two in the middle ; fourth longer than third ; last joint very short and conical. 

 Mentum* with three teeth much larger than the others ; between the central tooth 

 and each of the other large teeth are three small ones ; sides of mentum with four 

 to six long hairs. Last abdominal segment without ventral papillae. Anal sucker 

 with about 70 rows of hooks each containing 12-15 hooks about lO/u long. Anal gills 

 3, simple. Skin round anus beset with numerous minute scales dark in colour, and 

 plainly visible under a magnification of 100, split apically into a number of spines 

 (3-5). 



* Often incorrectly spoken of as the labium. 

 (713) r.2 



