364 NATURAL SCIENCE. Nov., 



happiness to the greatest number ; while, from another, she would 

 seem but to have set her heart upon devising and providing means by 

 which to torture and destroy the sentient creatures she has made. 



In this way, season by season, the greater part of the larvae of 

 insects, multitudinous often as the plague-flies of Egypt, are decimated 

 by other larva?, inquiline or parasitic — 



" The unbidden crew of graceless guests." — Virgil. 

 which live upon their juices, or so rob them of their food, that they 

 die of atrophy and inanition. 



To realise this more fully, let us follow some phases of the life- 

 history of Cynips kollari, the maker of the marble nut-gall. 



And here, at the outset of our enquiry, we are met by the fact 

 that no male member of this species has yet been discovered, the 

 entire genus (in its present more restricted sense) 20 is, in fact, believed 

 by Hartig and other competent observers 2I to be parthenogenetic or 

 agamic. Whether this is so or not remains, perhaps, an open 

 question. The evidence in its support is wholly negative ; and 

 though hundreds of thousands of galls of Cynips kollari have been 

 examined by ourselves and others with no result but that of yielding 

 females, the male element may nevertheless exist, and sooner or later 

 be found, as in the case of the oak-apple and other now well- 

 established instances, in a gall, differing in character, in date of 

 maturity, and in position, from that in which the female appears. 



Following, then, as we may now do, one of these presumably 

 agamic females, we find her in due season puncturing the young 

 buds of the oak, and depositing in each a single egg. 



This action, apparently so simple, becomes, as we have seen, the 

 initial factor in a series of organic perturbations, which result in the 

 production of a gall of a persistent and determinate character. Were 

 it not for our experience to the contrary, we might well believe that a 

 home so strongly fortified as this is, and so lavishly provisioned, 

 would, under all conditions of attack, hold out against invaders. This, 

 however, is far from being so. The cynips larva, though hidden away 

 in the very centre of the gall, is yet amenable to the incursions, the 

 attacks, of numerous cruel enemies, for whom its property and its life 

 become the necessary conditions of existence. 



Of these, two well-marked groups especially invite attention. 

 These are known as Inquilines and Parasites — the one phytophagous in 

 habit, living on the vegetable tissues of the gall ; the other entomo- 

 phagous, or insect-eating, preying on the juices of the living host, 

 which in this case feeds but to nourish the wolf within. 



Early in the development of the gall and the gall-insect, these 

 parasitic and inquiline enemies are alert and active. Guided by a 

 marvellous instinct, by a perfection it may be of smell, or subtlety of 



20 This genus comprises more than 50 species. 



- 1 See Beyerinck, " Beobachtungen liber die ersten entwicklungsphasen einiger 

 Cynipidengallen," p. 139 (Amsterdam, 1882). 



