560 HYMENOPTERA 



CHAP*^ 



little or no cruelty or acute suffering connected with this mode ol 

 life. The victim attacked is not eaten, the parasites in the in-| 

 terior taking in the lymph of the caterpillar either by the moutl 

 or by endosmosis, but not biting their host. The latter display 

 no sign of sickness, but eats voraciously, so that it serves merely 

 as a sort of intermediary between the juices of the plant and the 

 larvae inside itself It is only when the metamorphosis is at 

 hand that the host sickens, but this does not always happen : 

 parasitised larvae frequently change to pupae, and they may 

 occasionally even become perfect Insects. Cases are known in 

 which imagos have appeared with some of the small parasites 

 embedded in some of the outer parts of their bodies. These 

 cases are, however, very rare ; in the enormous majority of 

 instances the host is destroyed either when it is in the larval 

 stage or before the pupa has advanced to any great extent on 

 its metamorphosis to an imago. Particulars as to various species 

 will be found in the valuable work of Eatzeburg we have already 

 referred to.-^ Eeference may also be made to Goureau's account 

 of Microgaster glohatus^ this latter including some suggestions 

 by Dr. Boisduval on some of the difficult physiological questions 

 involved in the lives of these parasites. 



The metamorphosis of Microgaster fulvipes has been studied 



by Eatzeburg, and an epitome of his observations is given by 



Marshall.^ The larva goes through a series 



of changes somewhat similar to those we 



have already sketched in Anomalon cir- 



cumflexum. Usually these Insects after 



emerging from the body of their host spin 



a mass of cocoons more or less loosely 



connected together. A most curious case 



has, however, been recorded by Marshall^ 



of a stalked cocoon (Fig. 368) being 



Fig. 368. Stalked cocoon formed as an exceptional act by Apanteles 



f /p<^teies formosus. f^^^^Q^y^^^ Mr. Marshall has recently re- 



(After Marshall.) '^ -^ 



ceived other specimens of this cocoon as 

 well as the Insects reared therefrom in France, and inclines to 

 the opinion that the stalked cocoon may be the usual form, and 

 is sometimes departed from by the Insect for unknown reasons. 



1 Ichneum. Forst. Ins. 1844. 2 ^^^^ ^^g_ g^^_ France (2), iii. 1845, p. 355. 



'^ Tr. ent. Soc. London, 1885, pp. 224, 219. 



