OVIPOSIT ION 341 



whole development in the eggs of various insects. Certain of the 

 Encyrtidas and Eulophidae parasitise eggs of Lepidoptera or 

 Coleoptera, but complete their development in the larval stages of 

 their hosts. An enormous number of Hymenoptera parasitise 

 larvae only, or subsequently complete their development within 

 the pupae, while certain others are exclusively pupal parasites. 

 Parasites confined to imagines are less frequent, but the Braconid 

 genera Perilitus and Dinocampus are well known to parasitise adult 

 Coleoptera. 



The ovipositor is an instrument often used with extreme 

 accuracy ; as a rule the eggs are placed in the general body-cavity 

 of the host, but in other cases intra-organic oviposition prevails, 

 the eggs being laid in the fat-body, gut, salivary glands, brain or 

 other situations. The eggs as a rule are poor in yolk, or are almost 

 devoid of that material, while the chorion is thin or even mem- 

 branous or may be absent. After deposition the eggs frequently 

 increase markedly in size until eclosion of the larva supervenes. 

 Thus in the Ichneumon Meteorus dimidiatus the newly laid egg 

 measures 0-14 mm. x 0-04 mm., but it finally attains a maximum 

 size of 1-2 mm. x 1-5 mm. (Fig. 84) ; in Dinocampus rutilis, 

 another Braconid, Jackson states that the egg may increase in 

 cubic content over 1,200 times. The primary larvae frequently 

 emerge in a very early stage of ontogenetic development, they 

 assume great diversity of form and hypermetamorphosis prevails 

 {vide Chapter III.). The significance of the morphological features 

 thus exhibited is very obscure ; certain of them appear to be 

 inherited ancestral survivals, while some are most likely adaptive 

 in significance. In the final instars, however, the apodous maggot- 

 like type common to all Hymenoptera-Apocrita is assumed. The 

 chief features of endoparasitic life are discussed on pp. 343-353, 

 and consequently will not be referred to here. 



Among Tachinidae both subcutaneous oviposition and larvi- 

 position occur, and the species exhibiting the habit form groups 

 VII., VIII. and IX. of Pantel. The female fly is provided with an 

 instrument for perforating the integument of the host, and in its 

 most usual form, as exhibited in Compsilura concinnata, it consists 

 of a curved acutely pointed piercer which is grooved dorsally to 



