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Stricklaxu (E. H.). Further observations on the Parasites of 

 Simulimii Larvae. — Journal of Morpholuyij, xxiv, uu. 1, 

 20tli March 191;J, pp. 43-94, 6 pis. 



The author bases this paper upon observations of parasites of 

 Simulium larvae made during- the autumn of 1911 in the neigh- 

 bourhood of Boston, U.S.A. The streams there were found to 

 contain immense numbers of these larvae, the most abundant 

 species being" S. hutipes, which occurred in such vast masses that 

 in certain streams hardly a stone could be found which did not 

 support one or more colonies. Larg-e numbers of the larvae of 

 this, and those of an undescribed species were parasitised by 

 Microsporidians. By the middle of May all the larvae of the 

 generation under observation had pupated and hatched and during' 

 the summer few were to be seen in any of the streams ; onlj' here 

 and there did the author find an isolated specimen of the larva of 

 ^S'. hracteatum, Coq. Early in October the search was resumed 

 and the larvae of *S'. hracteatuin were found everywhere, though 

 always living' a solitary life; of S. vittatum a few specimens 

 occurred in one stream, *S'. Jiirtipes not being found until the 

 beginning of November, after which it was common in some 

 localities. By the middle of November it was difiicult to collect 

 larvae because the streams were filled with fallen leaves to which 

 the larvae attach themselves in preference to stones. 



The author describes and figures the larva and pupa of 

 ,S'. hracteatum and discusses certain structural peculiarities and 

 habits of Simulium larvae which bear on the subject of para- 

 sitism. These larvae are particularly difiicult to study in the 

 living condition because they cannot be kept alive for a sufficient 

 time in captivity, one of the principal reasons being that their 

 respiratory gills are very small and they are unable to obtain 

 the oxygen they rec^uire in sufficient quantity from stag-nant 

 water; in nature they live only in very rapidly flowing' water. 

 It is further a matter of interest that the majority of the pupae 

 of Simulium fail to hatch in captivity, probably owing to insuffil- 

 ciency of oxygen. 



The classification, typical life-cycle and general host relation- 

 ships of the Microsporidia are given, with a list of insects infested 

 by them. Several species of Microsporidia are described at 

 length. The probable mode of entry into the body of the host is 

 discussed and also the effect of the parasite upon the hosts, the 

 most remarkable of which appears to be the destruction of the 

 reproductive organs. These are easily found in sections of 

 healthy larvae, but the author says that in parasitised larvae 

 he was quite unable to find them. He is convinced that 

 parasitised larvae never reach the adult stage. He summarises 

 his results as follows : • — -That in the neighbourhood of Boston 

 there are three distinct classes of parasites infecting and in each 

 case killing SimuliuTn species in their larval stages : (1) Parasites 

 of the spring brood of Simtilium, of which various Mycvosporidic 



(2'J8G5— 2.) Wt. P 11— 1-2. 2000, .Vi:"-. D & 8. 



