L35 



THE EARLY STAGES OF CERTAIN WEST AFRICAN MOSQUITOS. 



By A. Ingram and J. W. S. Macfie, 

 West African Medical Service. 



(Plates I— IV.) 



Howard, Dyar and Knab in their monograph " The Mosquitoes of North and Central 

 America and the West Indies," in discussing the rearing of mosquitos, emphasise 

 the importance of larvae in specific determination. They write (Vol. I, p. 181) 

 " Many species of Culex are of uncertain determination without the associated larvae, 

 while some Aedes have identical adults, yet dissimilar larvae. The characters of the 

 larvae reside in the modifications of the chitinous appendages of the skin and the 

 arrangement of the hairs. As these are fully retained by the cast skins, it is possible 

 to preserve both the larva and the adult of the same identical specimen, thus assuring 

 absolutely correct associations." This plan has been carried out so far as possible in 

 the rearing of the mosquitos, the larvae of which — obtained during 1916 in Accra 

 and its vicinity — we have attempted to describe below. 



We take this opportunity of pointing out that so far as our experience of the 

 mosquitos of Accra goes, Howard, Dyar and Knab are in error in controverting the 

 statement of the late Sir Rubert Boyce that mosquitos living in crab-holes " are the 

 chief nuisance in those houses which are situated near the sea." Howard, Dyar and 

 Knab write : " Our observations prove that the crab-hole mosquitoes do not bite nor 

 annoy man and no consideration need therefore be given to their destruction." 

 In Accra Culex thalassius, Ochlerotatus irritans and Anopheles costalis are commonly 

 found nourishing in crab-holes, all of these mosquitos are vicious biters and invade 

 houses ; their destruction therefore is one of the problems which must be faced by 

 Sanitary Authorities on the West Coast of Africa, especially as A. costalis is a proved 

 carrier of malaria. 



We have here to express our indebtedness to Dr. A. C. Parsons, Junior Sanitary 

 Officer at Accra, and to Dr. J. B. Alexander. Medical Officer of Health at Accra, for their 

 untiring zeal in procuring for us specimens of larvae. Our thanks are again due to 

 Dr. G. A. K. Marshall, of the Imperial Bureau of Entomology, and to Mr. F. W. 

 Edwards, of the British Museum, for much help and advice and for identifying species. 



Anopheles marshalli, Theo. 



The head is small as compared with the thorax. The brushes are prominent. The 

 antenna possesses no hair-tuft and its surface is covered with minute spines, which, 

 however, are almost absent externally. At the end of the antenna there are stout 

 spines and a short branched hair ; this hair shows at least three branches. The 

 anterior frontal hairs (clypeal hairs) are all simple and appear to be placed in a triangle, 

 one being situated anteriorly and two posteriorly ; of the two posteriorly placed hairs 

 the external is only slightly in advance of the internal. The internal posterior hair 

 is nearly twice as long as the others. The mental plate is small and carries a median 

 tooth with four teeth on either side. 



