Februabt 4, 1910] 



SCIENCE- 



195 



this principle to the large number of phe- 

 nomena in aqueous solutions which so well il- 

 lustrate the laws of chemical equilibrium. 



The student who depends upon this text- 

 book may acquire a large number of useful 

 chemical facts. He will be attracted by the 

 lucidity and stimulated by the enthusiasm of 

 the author, but he will nevertheless be seri- 

 ously handicapped when in any field of chem- 

 ical endeavor he enters into competition with 

 men who are trained in the use of all the tools 

 of modern chemistry. Gilbert N. Lewis 



Massachusetts Institute of 

 Technologt, Boston, Mass., 

 January 20, 1910 



lagttagelser over Entoparasitislee Muscide- 

 larver hos Anthropoder. Af I. C. Nielsen. 

 Copenhagen. 1909. Entomologiske lled- 

 delelser, E. 2, Bd. 4 (1909), with 4 plates. 

 The above paper consists of 110 pages in 

 Danish of investigations of muscid-larvse ento- 

 parasitie on arthropods, exclusive of careful 

 explanations in both English and Danish of 

 the plates and over five pages in English 

 giving a summary of the more important 

 results announced. It shows much pains- 

 taking work, and the author is to be highly 

 commended on the very valuable results ob- 

 tained. 



After reviewing the greater part of the 

 literature, eight species are treated in detail, 

 descriptions and figures being given of the 

 maggot stages and puparia, to which are added 

 many data on host relations. The one great 

 feature of the work is the establishing of 

 definite characters in the pharyngeal skeleton 

 of the eight species studied, whereby the 

 maggot stages can be accurately determined. 

 It is reasonable to suppose that the characters 

 given by the author will hold good through 

 a large part of the superfamily Muscoidea. 

 Excellent figures are given of the pharyngeal 

 skeleton in its different stages, and the au- 

 thor is undoubtedly correct in assuming that 

 there are but three maggot stages in the 

 majority of the Muscoidea. Some exceptions 

 to this rule may yet be found, though it must 

 be admitted that the probability of such is 



remote. Investigations carried on by the 

 bureau of entomology at the gipsy moth 

 parasite laboratory in Massachusetts indicate 

 that much further study of the subject is 

 needed. 



The spiracles of the maggot, both anterior 

 and posterior, have been carefully studied and 

 figured by the author. The determinations of 

 the eight species above mentioned were made 

 with the aid of Mr. H. Kramer, the German 

 specialist in Tachinidae. I can only say that 

 two of them, Taclnna larvarum Linn, and 

 Carcelia gnava Meig., are not the species 

 handled by us under those names at the lab- 

 oratory, and we have the authority of Drs. 

 Kertesz and Handlirsch for our determina- 

 tions. Nielsen's larvarum deposits maggots, 

 while ours deposits eggs. As further evidence 

 that we are right, we know that the American 

 and Japanese species of Tachina deposit eggs. 

 The anal stigmata of the puparia of our 

 larvarum and gnava differ conspicuously from 

 those figured by Nielsen under these names. 

 These points only show the difficulty of arriv- 

 ing at uniform determinations in the Tach- 

 inidas with our present knowledge; careful 

 study and comparison of types, even of the 

 most common species, must be made. 



Another point of importance brought out in 

 the paper is the fact that the chitinous funnel 

 of the maggot is not an actual part of the 

 latter's integument, but is formed to a large 

 extent from the integument of the host. The 

 author shows that this funnel is present in all 

 three stages of the maggot of certain species, 

 but we know that other species are without it 

 in the first stage. 



Doctor Nielsen is certainly mistaken in be- 

 lieving that Compsilura concinnata does not 

 penetrate the skin of the caterpillar with its 

 piercer at the moment of larviposition. Our 

 investigations, including actual observation of 

 the living flies and dissection of both flies and 

 hosts, prove conclusively that such penetration 

 takes place. There is a considerable group of 

 species, both European and American, that 

 have this habit. Mr. William E. Thompson 

 has recently secured thorough demonstration 

 of the fact with concinnata at the laboratory, 

 thus verifying conclusions arrived at from a 



