1915.] 221 



to the pale stigmata, there is a pale band on the hind-margin of the fore-wings ; 

 in fig. 4 the pale marginal band is extended into a series of rays some half- 

 way across the fore-wings, and which Warnecke designated as ab. albingensis ; 

 in fig. 5 the moth is iiniformly black, without any trace of pale marking. 

 Altogether the forms mvist be very beautiful and striking. Dr. Hasebroek con- 

 siders the variation as probably due to smoke. Unfortunately C. or does not 

 appear to occiu- in the chief areas of melanism in Britain, the smoky districts 

 of South-west Yorkshire and Lancashire, or probably similar conditions woxild 

 have produced these melanic forms in our own country. — Geo. T. Pobbitt, 

 Huddersfield : June 3rd, 1915. 



Jibstracts of |U'renl literature. 



BY HUGH SCOTT, M.A., F.L.S., F.E.S. 



Thompson, W. R. (i) "The Cuticula of Insects as a Means of Defence 

 AGAINST Paeasitbs." Proc. Camb. Phil. Soc, Vol. 18, part 2, pp. 51-55, 1915. 



(ii) " Les conditions de la eesistancb dbs insectes parasites in- 

 ternes dans e'crqanisme de leurs hotes." C. E.. Soc. Biol. (Paris), Vol. 77, 

 pp. 562-4, December, 1914. 



(iii) " SuR UN Diptere parasite de la larve d'un Mtcetophilide," 

 Op. cit.. Vol. 78, pp. 87-9, 1915. 



(iv) " SuR TINE TaCHINAIRE PARASITE A STADB INTRACUTICULAIRE." 



C. R. Ac. Sci. (Paris), Vol. 160, pp. 83-85, 1915. 



The writer of these articles, who is at present working in the Zoological 

 Laboratory of Cambridge Universitj', is devoting much stvidy to various 

 biological qxiestions connected with entomophagoiis parasites, in particular 

 Tachinidae. The fii'st paper commences with an allusion to certain views 

 which have been expressed on the question at issue. Metchnikoflf has suggested 

 that the phagocytic reaction to parasites is rather feeble in Arthropods, and 

 that this may be correlated with the presence of the chitinous cuticle, which 

 prevents entry of internal parasites, and thereby rendeis ivjiuceessary a strong 

 phagocytic reaction. An opposite view has been taken by Cuenot, who has 

 pointed out that, far from the chitinous cuticle preventing entry of parasites. 

 Arthropods are the most heavily-parasitised group : he considers that the para- 

 sites escape destruction by the phagocytes of the host, not through the feeble- 

 ness of the phagocytes, but by adapting themselves to resist them. 



Thompson has collected certain data which appear to favoui- Metchnikoff's 

 view to some extent, in that the chitinous cuticle of the host does prevent the 

 entry of a large percentage of individuals of a parasite species. Tachinidae 

 are very interesting in this connection, since they have not, like many parasitic 

 Hymenoptera, a powerful ovipositor with which to introduce their eggs into 

 the host, but their new-hatched larvae must make their own way from the 

 exterior through the host's integument. In the case of a Tachinid parasitic on 

 caterpillars of the Gipsy Moth in the United States, he has observed that 

 the newly hatched larvae are sometimes quite unable to bore through the 

 cuticle of the host ; and though many of the caterpillars bear on their bodies 



