Miscellaneous Pests. 



550 



[June, 1909. 



The larvae, or mosquito wriggler is 

 early distinguished from all other forms 

 of water insects. The pupa is somewhat 

 like the larvae. It moves about actively in 

 the water, but is darker than the larva, 

 and tne 'head 'is much larger in propor- 

 tion. What appears to be the 'head' is 

 really the head and thorax, and the 

 greatly increased size is due to the deve- 

 loping mouth parts, eyes, and antennaB 

 on the head, and the wings and legs on 

 the thorax. When the development 

 inside the pupa is complete the imago (or 

 adult) emerges, and shortly afterwards 

 the process of egg-laying begins. 



During all this process of change and 

 development, the mosquito is exposed 

 to the attack of its enemies. The adult 

 mosquito on the surface of the water 

 in the process of egg-laying, the eggs 

 during the several days before they 

 hatch, the larvae wriggling from the 

 bottom to the surface to breathe, the 

 pupae and even the newly-transformed 

 adults emerging from the pupa cases 

 at the surface, — are all liable to repeated 

 attack. 



Breeding Places op Mosquitos. 

 The Anopheles mosquito which disse- 

 minates malaria does not occur in Barba- 

 dos. The argument has been advanced 

 that the piesence and abundance of 

 millions in Barbados account for the 

 entire absence of the malarial mosquito 

 from the island. This argument is sup- 

 ported by the fact that the natural 

 breeding places of the malarial mosquito 

 are inhabited by millions, It has been 

 found by those who have investigated 

 the subject that Anopheles breeds only 

 in fairly permanent natural pools at or 

 near the ground-level, while Culex and 

 Stegomyia breed freely in small collec- 

 tions of water in all sorts of receptacles. 

 Rainwater tanks, cisterns, reservoirs, 

 broken pots, bottles, ard old tins are 

 inhabited by these two, and they breed 

 even in the gutters on the roofs of 

 houses, if a sufficient amount of water 

 remains standing there. 



In India it has been found that while 

 the species of Culex generally breed in 

 vessels of water around the houses, the 

 species of the genus Anopheles breed in 

 small pools of water on the ground. 

 In Sierra Leone it was found that while 

 " Culex larvae were to be seen in almost 

 every vessel of water, or gourd, or 

 flower-pot in which a little rainwater 

 had collected, in only one case were 

 Anopheles larvae found in such recep- 

 tacles. On tbe other hand they occurred 

 in about 100 small puddles scattered 

 throughout the city of Freetown— pud- 

 dles mostly of a fairly permanent descrip- 

 tion, ke"pt filled by the rain, and not 



liable to washing out during heavy 

 showers. It was noticed also that the 

 larvae seemed chiefly to feed on green 

 water weed." 



It is stated that at "Freetown not 

 only do the larvae of Anopheles exist 

 in the small pools in the rocks, but also 

 in the pools by the sides of streams and 

 in certain small drains. In the dry 

 season, in the absence of the rock pools, 

 Anopheles breed freely in streams and 

 drains, and the adults exist in most 

 parts of the town in dwellings, espe- 

 cially in overcrowded native huts and 

 native quarters, ready to lay their eggs 

 when pools appear. Outside the city, 

 in the 'bush,' Anopheles larvae were 

 present throughout the whole district. 

 In the mountain streams, wherever there 

 were suitable pools, multitudes of larvae 

 existed. In tracing the mountain 

 streams, occasionally for H miles or so, 

 no larvae were found, but then a rock 

 pool occurred, and there they were found 

 in numbers. At Sango and Nabang 

 Anopheles larvae were detected in the 

 swamps. They were not present in the 

 main swamp water on account of the 

 innumerable small fish but were occasion- 

 ally observed in small isolated pools 

 on the mud, and were still more com- 

 mon in small pools afc the edges of 

 swamps." 



It has been stated that at St. Lucia 

 Anopheles do not deposit eggs anywhere 

 except close to the ground-level, but 

 there is no definite statement that the 

 larvae have not been found in broken 

 bottles, old tins, flower pots, etc. 



In Antigua, it has been observed that 

 Culex and Stegomyia larvae are found 

 in tanks, cisterns, and other receptacles, 

 while Anopheles larvae are found only 

 in shaded streams and ponds. 



The fact that water in which millions 

 live remains free from mosquito larvaB 

 is due mostly, if not entirely, to the 

 way in which these fish feed, and not 

 to what they feed on. They vigorously 

 attack small insects that are drowning 

 or resting on the surface. It is probable 

 that mosquitos attempting to lay eggs 

 on the water are captured and eaten, or 

 disturbed to such an extent as to prevent 

 them from laying their eggs where 

 millions aie present. 



The statement that millions feed in 

 Barbados on the larvae of Anopheles can 

 hardly be taken as correct, for it has 

 not been proved that Anopheles have 

 ever bred in this island. From the 

 avidity with which they attack the 

 larvae and pupae of Culex and Stegomyia, 

 however, it seems likely that they would 

 attack the larvae of Anopheles in the 

 same way. 



