GECIDOMYIA. 183 



that period. Winnertz observed an extraordinary activity in some 

 such larvae after a thunder storm ; they left their hiding-places un- 

 der ground, and crawled about restlessly for some time; they did 

 the same after every thunder storm, some of them even two months 

 after having left their galls. 



The larvse of several species, for instance, Gee. loti, Gee. pisi, 

 and Gecid. rumicis, have the power of leaping. Mr. Loew remarks 

 that all such larvae belong to the sub-genus Diplosis. Gee. populi 

 Duf. performed its leaps by straining the horny hooks at the tip 

 of its abdomen against the under side of the thoracic segments. 

 (Dufour, Ann. Sc. Nat., 2e ser. XVI, p. 257.) 



" The want of horny organs of mastication," says Mr. Winnertz, 

 "authorizes the supposition that a lesion of the plant does not take 

 place ; it is much more probable that the larva has the power of 

 producing in the plant some peculiar irritation, which causes an 

 overflow of the sap necessary for its food. How little the larva 

 requires for its support is evident from the circum&tance that it 

 attains its full growth and development in a gall just large enough 

 to inclose it, a gall apparently hermetically closed, for the most 

 part with hard walls, which do not show the least sign of internal 

 lesion. It seems even as if a certain amount of moisture alone 

 was sufficient to sustain these larvae, especially when a great num- 

 ber of them live socially in the same gall (from ten to fifteen larvae 

 in the pea-sized bud .of Gardamine pratensis; from fifty to sixty 

 in another kind of gall, etc.). Another proof of the small quan- 

 tity of nourishment required by these larvae is, that no excrements 

 are to be found in their place of abode." 



"The only exception known to me of this extreme frugality," 

 says the same author, " are the larvae of two species which live on 

 the leaves of the white rose, attacked by the fungus Geoma minia- 

 tum. These larvae not only lick the sap exuding at the bottom of 

 the heaps of spores, but they also greedily consume the spores 

 themselves, and their intestinal canal is always filled with them." 



The observation of Yallot (Mem. de Dijon, 1827, p. 95), that 

 a larva of Gecidomyia (G. aearivora) found on the surface of the 

 leaves of Chelidonium feeds by sucking Acari, as yet requires con- 

 firmation. Winnertz saw Gecidomyia-lsiYYse living as guests in 

 deformations produced by Acari, greedily lick their hosts, but he 

 never found in such galls an empty skin of an Acarus. As to the 

 larvae of Gecidomyia inhabiting galls, produced by other species 



