57 



however usually delayed and. if it does occur, the mosquitos die, since 

 the pupae are unable to survive without direct access to free air. Thus 

 it is evident that in practice, oiling is less successful than it theoretically 

 should be, because many species of larvae spend a considerable part of 

 their time at the bottoms of ponds and some may remain submerged 

 long enough to allow a most liberal application of kerosene to evaporate. 

 The particular effect of the application of crude kerosene to fluids 

 containing various species of mosquito larvae is given. The larvae so 

 treated included those of Anopheles costalis, Culexjfatigans, C. invidiosus, 

 C. thalassius, Mansonioides africanvs and S.fasciata. The first three 

 species are easily destroyed by oiling. C. thalassius is less readily 

 killed, as, though the larvae are susceptible to the action of kerosene 

 when they come in contact with it, they are capable of surviving for a 

 long time without coming to the surface to breathe. The larvae of 

 Mansonioides ajricanus usually obtain the oxygen they require by 

 thrusting their siphon tubes into the roots of the water weed, Pistia 

 stratiotes, but under laboratory conditions behaved in the same way 

 with other plants when this species was not available. These larvae 

 have been known to develop and pupate under a thick film of kerosene 

 and it was not until the pupa was almost ready to hatch and became 

 free from the weed that it was found dead in the oil on the surface. 

 Two further experiments on larvae of S. fasciata are described which 

 confirm the results of the experiment recorded at the beginning of the 

 paper and show that unless the layer of kerosene be sufficiently thick, 

 they may be able to survive long enough for the film to have evaporated. 



MacFie (J. W. Scott). Morphological Changes observed during the 

 Development of the Larva of Stegomyia fasciata. — Bull. Entom. 

 Research, London, vii, no. 3, January 1917, pp. 297-307, 7 figs. 



Descriptions are given of the structure of the various parts of the 

 larva of Stegomyia fasciata at each of the four phases of the larval stage, 

 which was found to average 13 days. For purposes of identification 

 the phase of development to which the larvae have attained must be 

 known, and for purposes of classification it is best to deal only with 

 those of the last or fourth phase, when they are easy to recognise. 

 Certain characters are constant throughout the larval period and other 

 features seem to undergo a regular and progressive development as the 

 larva matures. In addition, a few characters are peculiar to the earliest 

 phases, some of these possibly indicating some earher stage in the 

 evolution of the species. A comparative study of the changes found 

 in successive larval stages in other mosquitos might be of great 

 assistance in formulating a natural system of classification. 



Bodkin (G. E.). Report of the Economic Biologist. — Rept. Dept. Sci. 

 & Agric, British Guiana, for the Nine Months ended 31st December 

 1915 [Georgetown], 12th July 1916, pp. 8 & 9. [Received 

 27th February 1917.] 



For the control of cockroaches the use of traps baited with molasses 

 and stale beer and poisoned baits consisting of equal quantities of 

 molasses and boracic acid are recommended. These insects seldom 

 seriously infest houses which are kept thoroughly clean and especially 

 those in which all food is kept in well-made safes completely excluding 



