INSECTS INJURIOUS TO MAN AND STOCK IN ZANZIBAR. 395 



Culex laurenti, Newst. Larvae abundant in swamps and water-holes, often in 

 association with A. costalis. 



Culex decens, Theo. Larvae have been taken in various breeding places, such as 

 old tins, water-holes, road puddles, etc. 



Culex univitiatus, Theo. Larvae from rice swamps in association with AnopJieles 

 funestus. 



Culex sitiens, Wied. A common species ; adults have been captured in native 

 huts in numerous villages. 



Culex duttoni, Theo. Has a wide distribution. The larvae are easily recognisable 

 by the dark ring near the apex of the siphon and its peculiar torpedo-like shape. 



Culex perfusciis, Edw. Adults were captured in a cell in the central jail, the females 

 being heavily engorged with blood. The jail is outside the town. 



Culex sitnpsoni, Theo. Larvae were found in swamp water in company with a 

 large number of other species, including Anopheles costalis. 



Culex insignis, Cart. One record from a swamp area outside the town. 



Culex tritaeniorhynchus, Giles. One record from an area outside the town. 



Culiciomyia nebulosa, Theo. An extremely common form, and a very troublesome 

 biter ; larvae have been obtained from swamps and domestic utensils. A constant 

 characteristic of the larva seems to be the six pairs of hair- tufts on the siphon. 



Ochlerotatus pembaensis, Theo. Adults have been taken all along the sea-shore 

 for several miles in proximity to the town ; they are virulent biters. In Weti, the 

 capita] of Pemba Island, they are one of the commonest house mosquitos. Larvae 

 abomid in crab-holes and depressions close to high-water-mark, and are able to 

 withstand a high degree of salinity ; I have never found them actually in sea- water. 

 Experimentally they thrive in water to which 80% of sea-water has been added. 

 This species seems to be confined to the sea littoral, as we have no records of larvae 

 from inland waters. The larvae are long-lived and grow slowly, the average length 

 of life under normal conditions being 12 to 14 days. The characters of the larva 

 are as follows : — 



Head small, light brown in colour, with one small plumed hair above the eye. 

 Antennae long, cylindrical, with hair-tuft on the dorsum of the basal joint and single 

 long hairs at its apex. Thorax with long plumose hairs ; the median tufts set in 

 chitinous sclerites are remarkably long, being easily visible to the naked eye, and 

 help to distinguish this form in a mixed collection. Abdomen with long plumose 

 hairs on the first two segments, the remainder with single hairs. Comb difficult to 

 see, triangular in outline, with a large number of pronged teeth. Siphon about as 

 long as the 7th and 8th abdominal segments, not markedly pointed ; pecten with 

 12 teeth, the 6 basal ones short. Anal segment furnished with a broad prominent 

 beard composed of 8 long plumes. 



Ochlerotatus durbanensis, Theo. A small series bred from larvae obtained from 

 a rain-water pool in the neighbourhood of the to\vn. 



Ochlerotatus nigeriensis, Theo. Larvae obtained from rain pool in association with 

 A. costalis. 



