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SCIENCE 



[N. S. Vol. XXXIX. No. 993 



the nutritive instincts, a conception which 

 necessarily leads to a rather narrow and dis- 

 torted treatment of this multiform phenom- 

 enon. The insects that feed on other animals 

 are divided into three groups : typical pre- 

 dators (Eaptoria) parasitoid praedators (Para- 

 sitoidea) and true parasites (Parasita). The 

 parasitoids include such forms as the so- 

 called " parasitic " Hymenoptera, namely, the 

 chalcis-flies, ichneumons, etc., which in their 

 larval stage feed on the eggs, larvae or pupae 

 of other insects, but as adults do not depart in 

 structure from the non-parasitic members of 

 their order, whereas the Parasita live even as 

 adults on the bodies of certain hosts and also 

 in this stage exhibit modifications of struc- 

 ture which adapt them to their peculiar life. 

 At first sight this classification seems to be 

 very satisfactory, but it breaks down on closer 

 examination. If it were adopted one would 

 have to classify the male Strepsiptera as para- 

 sitoids and their females as parasites. More- 

 over, Eeuter's conception of parasitism is too 

 narrow, because it includes only food para- 

 sitism and excludes phoresy (which Eeuter, 

 for some unknown reason, writes " Foresie ") 

 and brood parasitism. Eeuter is, in fact, 

 compelled to expand and modify his concep- 

 tion of parasitism as soon as he conies to 

 consider the parasitic wasps and bees. 



Commensalism, and more especially mutual- 

 ism, are also somewhat too narrowly restricted 

 by their inclusion under the nutritive in- 

 stincts. Various forms of the migratory in- 

 stinct are likewise considered under this head, 

 as are also the various methods adopted by in- 

 sects in protecting themselves from competing 

 consumers. This latter subject forms a tran- 

 sition to the protective instincts proper. It 

 is interesting to note that Eeuter treats the 

 toilet instincts (" Eeinlichkeitsinstinkte ") as 

 protectives, since they have a sanitary value, 

 no less than the methods of protecting the 

 organism against excessive cold, heat, mois- 

 ture, etc. Protection against enemies is dis- 

 tinguished as passive and active, the former 

 comprising the cryptobiotic instincts (in the 

 sense of Willey), protective coloration, 

 mimicry, etc., the wonderfully diverse meth- 

 ods of forming the larval and pupal cases, 



autotomy and "death-feigning," while the 

 actively protective behavior includes the use of 

 the repugnatorial glands, the peculiar phe- 

 nomena of " autohaemorrhoea," or emission of 

 poisonous blood (often charged with canthari- 

 din) from the joints of the legs in various 

 larval and adult beetles, and phosphorescence, 

 although this is in some cases passive (larval 

 fire-flies) or connected with courtship (adult 

 fire-flies). Eeuter's treatment of the much- 

 discussed subjects of protective resemblance 

 and mimicry is very conservative. Any con- 

 sideration of the many doubts which have 

 been cast on these subjects by recent authors, 

 especially in continental Europe, is omitted, 

 as we should expect from the author's assump- 

 tion that protective colors and devices are 

 essentially passive, instead of being the stable 

 results of once active adaptations. 



Eeuter devotes to what he calls the " in- 

 stincts of metamorphosis " a chapter including 

 the peculiar larval activities which leave the 

 pupa in situations best adapted to the eclosion 

 of the adult insect. This chapter clearly 

 shows how impossible it is to draw a hard and 

 fast line between the general physiological 

 and morphological processes, on the one hand, 

 and the instinct activities, on the other. 



The reproductive instincts include the phe- 

 nomena of courtship, that is, the exhibition by 

 one sex of its peculiar movements, colors and 

 structures, photogenesis, the use of the osma- 

 teria, or scent-glands, and such extraordinary 

 pieces of behavior as that of the balloon- 

 making male Empidid flies described by 

 Girschner, Mik, Aldrich, Hamm and others. 

 and finally oviposition and the extension of 

 maternal and in rare cases also of paternal 

 care to the eggs and larvae. 



The discussion of these and the foregoing 

 subjects occupies about two thirds of the 

 volume; the remainder is devoted to an ex- 

 cellent summary of the habits of the solitary 

 wasps and solitary bees, and closes with two 

 chapters on the adumbrations of social life 

 noticeable in some non-social insects. The 

 peculiar mixed arrangement of the materials 

 relating to the wasps and bees is evidently 

 intended to call attention to the parallelism or 

 convergence in the phylogeny of their habits. 



