ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 555 



hereditary constitution of an animal on that of a plant, in the sense 

 that factors associated with the insect determine the form-character 

 locally, rather than those normally associated with the plant's germ- 

 plasm. These latter plant factors suffer suppression. 



In conclusion, the author suggests that zoocecidology affords a 

 hitherto unrecognized field for the study of problems pertaining to the 

 mechanism used in the expression of hereditary characters. 



Hessian-fly Parasites.* — C. M. Packard contributes a paper of much 

 economic importance on the life-histories of three parasites of the 

 Hessian-fly {Mayetiola destructor Say) and methods of rearing them. 

 The species are Eupelmus altynia French, Merisus destructor Say, and 

 Micromelus suhapterus Riley. Parasites are the most effective factors in. 

 the control of the Hessian-fly, and the author says that " a thorough 

 knowledge of the life-liistories, field-habits, relative efficiency, and 

 effective methods of artificial propagation and dissemination of the 

 different parasites, therefore, might make it practicable to introduce the 

 most efficient species from localities where tliey are abundant into other 

 localities where the host is working destruction unchecked by its 

 enemies." To this end methods of breeding and rearing the three 

 species are given, and tlieir life-histories are traced through the egg, 

 larva, pupa, and adult. Figures are given of the eggs, pupge, and larv®^ 

 much enlarged, and of the mandibles of the full-grown larvaj, highly 

 maguified. 



Position of Jassoidea.f — Eric S. Cogan has made a morphological 

 study of the super-family Jassoidea, small, or comparatively small, 

 Homopterous insects which have prismatic hind tibiag armed with a row 

 of spines on their posterior margins. The super-family is divided 

 according to the position of the ocelli and the venation of the elytra 

 into Bythoscopida3, Tettigoniellidae, Jassid«, and Typhlocybida. 



Cogan finds that the Jassoidea can be homologized with the other 

 Homopterous families. The head differs very little from the funda- 

 mental plan of the Cicada, and while the Jassid does not show the 

 prominent sulci the mouth-parts are very similar. The mandibular 

 setaB represent the mandibles ; the maxillary sette together with the 

 maxillary plate constitute the maxilla;. The labrum and clypeus are 

 scarcely distinguishable from one another ; the epipharynx is closely 

 related to the labrum. The tentorium is present, and the invaginations 

 occur as in all insects. There is a well-developed salivary pumping 

 apparatus. The epicranium is subject to some modification in size. 

 There is a well-developed nervous system, almost entirely in the head 

 and thorax. The digestive system agrees in the development of a food- 

 reservoir with the other Auchenorrhynchous Homoptera. In general^ 

 the internal structure is that of a generalized Hemipteron, and the 

 various modifications which occur are just as likely to be specific as well 



as generic. 



* Journ. Agric. Research (Washington), vi. (1916) pp. 367-81 (2 pis.). 

 t Ohio Journ. Sci., xvi. (1916) pp. 299-322 (3 pis.). 



2 Q 2 



