Forest entomology . etterhan—viz., the much greater facility afforded to the indirectaction through insects, by the enormously more rapid succession ofgenerations with the latter than with many of their vegetable hosts—oaks above all (Nature, vol. xli. p. 394). This difficulty,however, Mr Cockerell believes may be surmounted by the con-sideration that a growing plant need not be regarded as a singleindividual, but rather as an assemblage of such (vol. xli. , 560). With regard to the insects producing oak galls, the transformations 138 FOREST ENTOMOLOGY. of the Cynipidse are complete. The
Forest entomology . etterhan—viz., the much greater facility afforded to the indirectaction through insects, by the enormously more rapid succession ofgenerations with the latter than with many of their vegetable hosts—oaks above all (Nature, vol. xli. p. 394). This difficulty,however, Mr Cockerell believes may be surmounted by the con-sideration that a growing plant need not be regarded as a singleindividual, but rather as an assemblage of such (vol. xli. , 560). With regard to the insects producing oak galls, the transformations 138 FOREST ENTOMOLOGY. of the Cynipidse are complete. They pass through four stages—viz.,egg, larva, pupa, and imago (fig. 129). The egg (fig. 129, a) is pyriform, with one end elongated, terminat-ing as a prolonged penduncle. Adler supposed the function of thisorganism to be respiratory, it having long peduncles when deeplyembedded and difficult of access to oxygen, and shorter when accessis easy. The eggs of the Cynipidse are often laid in winter, thus contrasting. a Egg of Cynips. (Copied from Adler and Stratton.)b Larva of Pupa of Gall -fly, Teras teriniwtlis (oak-apple). Male. (From photograph.) e Ovipositor of Neuroterus Icnticularis. (From camera-lucida sketch.)/ Wing of Spathegaster baccarum. (From photograph.)g Antenna of Spathegaster baccarum. (From camera-lucida sketch.) with the eggs of many species of saw-flies, which are deposited whennature is active. There are other interesting points about the eggswhich will be considered later on. The larvae are white, footless, and fleshy grubs, with thirteensegments (fig. 129, h). There is considerable diversity of time regard-ing the larval stage. In appearance the pupae are similar to the larva?, and some organsof the perfect insect are discernible. Fig. 129, c. HYMENOPTEllA OAK GALLS. 139 The imagines, apart from the salient features to be consideredunder general anatomy, present very few interesting habits. Theyare inactive, take no food, but are known
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