195 



Hadwen (S.)- The seasonal prevalence of Eypodenna bovis in 1915, 

 together with observations on the terrifying effect H. bovis has 

 upon cattle, and lesions produced by the larvae. — 46th Ann. Rept. 

 Entom. Soc. Ontario, 1915, Toronto, 1916, pp. 108-119, 4 figs. 

 [Received 10th October 1916.] 



At Agassiz, British Columbia, tlie seasonal activity of Hypoderma 

 bovis extended from the beginning of June to the beginning of August, 

 in 1915. The last larvae to emerge from the backs of cattle did so 

 during the first days of July. As an average of all the records of the 

 pupal stage (except Carpenter's record of 8 weeks in 1914) gives 35 

 days, the season for flies cannot extend far into August. High temper- 

 atures shorten the pupal period ; when larvae of H. bovis were placed 

 in an incubator at 80° F., the flies emerged in from 16 to 19 days. 

 The situation in which the larva finds itself on leaving its host also 

 makes some difference. Crevices in the floors of stables, etc., must be 

 warmer than the outside air. Such situations would mainly favour 

 H. lineata and the early larvae of H. bovis, and it is quite possible 

 that some of the early appearances of the former may be accounted 

 for in this way. The terror inspired in cattle by H. bovis is due to its 

 persistence in attack and the manner in which it oviposits. As' it 

 only lays one egg at a time, it is able to do so regardless of the move- 

 ments of the animal, but the distribution of the eggs is consequently 

 more irregular than in //. lineata. Hewitt's observations on 

 the penetration of the skin by the larvae of H. bovis [see this Revieiv, 

 »Ser. B, iii, p. 19] are confirmed. The passage of H. bovis larvae was 

 proved by cutting circles in the hair round newly laid eggs, and later, 

 after the eggs had hatched, by finding the swellings underneath. 

 These swellings are somewhat different from those of H. lineata, as 

 there is less exudation of serum, and they seem rounder and more 

 raised. They are usually about half an inch in diameter, but if several 

 eggs are laid close together, the swellings may merge into one another. 

 In H. lineata, it is probable that several larvae choose the same follicle 

 for entrance, seeing that a number of eggs are attached to the same 

 hair. The eggs nearest the skin hatch first, and it would seem probable 

 that the larvae follow one another through the same opening. The 

 result would be a larger opening than the single larva of H. bovis 

 could make, and consequently a bigger flow of serum occurs. The 

 sv\'elliugs in the case of H. bovis are sometimes quite large, but there 

 is not so much dermatitis or exfoliation of the skin. One remarkable 

 fact was noted in regard to both species of larvae : the swellings and 

 skin lesions are confined almost entirely to the older animals, the 

 calves only showing slight effects. This natural immunity breaks 

 down with age and is all the more interesting because young cattle are 

 more heavily parasitised than older individuals. 



Legendre (J.). Destruction des Moustiques par les Poissons. [Destruc- 

 tion of mosquitos by fish.] — C.R. Hebdofn. Acad. Sci., Paris, clxiii, 

 no. 15, 9th October 1916, pp. 377-378. 



A station has been estabhshed at Antananarivo, Madagascar, for 

 the purpose of breeding two varieties of carp which feed on AnopheUne 

 larvae and which have been imported from France and from Reunion 

 respectively. Observations on another introduced form, Carassius 



