THE GENERAL SUBJECT. 
227 
Specific gravity of insects. The same author commiinicates (Ann. N. II. 
4, X. pp. 55-57) an abstract of his researches in Arch. Sci. Nat. xliii. (1872) 
upon this subject. His conclusions are so varied, and of so little practical 
use to entomologists, that it seems unnecessary to do more than indicate the 
existence of the work. As an instance of the apparent impossibility of 
defining any standard as to the centre of gravity in insects, it may be ob- 
served that in Dragonfiies, of nearly the same external aspect, the relative 
positions of the centre in the same sex vary from the posterior margin of the 
metathorax to the first third of the 3rd abdominal segment. G. Vimercati, 
Bull. Ent. Ital. iv. pp. 188-200, gives a general notice on this subject, 
recapitulating Plateau's experiments and their result (Table, p. 196). 
M. Girahd's ' J^tudes sur la chaleur libre degagee par les animaux inver- 
tebres et specialement des Insectes ' (Paris : 1869, 4to, reviewed in R. Z., 2, 
xxii. p. 35 et seq. : cf. Gerstacker, Ber. Ent. in Arch. f. Nat. xxxix. Bd. iii. 
p. 2) has not been seen by the Recorder. 
The male element in insects indirectly connected with defective vitality. 
C. V. Riley, Am. Nat. vi. p. 692. 
Parthenogenesis. A notice in Bull. Ent. Ital. iv. p. 384 etseq., by Siebold, 
under the head "Intorno alia partenogenesi riconosciuta nelle Farfalle di 
antichi Italiani," although relating to Lepicloptera more particularly, may be 
noted here. The observations of Castellet, Reaumur, Rossi, and Ochsenheimer 
are quoted. 
Insects and birds. The conclusions of Edouabd Perms (M^m. Li^ge ; re- 
viewed in Nou 7. et Faits, p. cxlv) are : — 1, that birds only congregate at the epochs 
of migration, when most insects are comparatively rare ; and when insects are 
in masses, birds are isolated ; 2, that although birds destroy large quantities 
of insects, the really noxious species of these are in comparatively very small 
numbers, and in destroying them much vegetable produce and useful insects 
are also destroyed ; 3, that the most destructive insects are in various ways 
protected from attacks by birds ; and, 4, that larvae, which are especially 
noxious, are especially protected. 
Injury to agriculture: cf. observations by Ghiliani, Bull. Ent. Ital. iv. p. 32 ; 
Piccioli!i ibid. p. 226; Tozzetti, ibid. p. 228 ; cf. also pp. 316-319. 
Plant-fertilization. T. H. Farrer, " On the fertilization of a few common 
Papilionaceous flowers," Nature, vi. pp. 478-480, figs. 1-8, pp. 498-501, figs. 
9-17. C. J. Hayden, ibid. p. 60 (Dictamnus). W. 0. Marshall, ibid. 
p. 393 {Lepidoptera). Thos. Meehan, On the agency of Insects in ob- 
truding evolution," P. Ac. Philad. 1872, pp. 235-237, chiefly from an ex- 
amination of variations in Linaria vulgaris, comes to the conclusion that 
insects are " not always abettors, but rather at times conservators, of advan- 
cing evolution." 
Insects shaped by the needs of flowers : C. V. Riley, Rep. Amer. Soc. 
Adv. Sci. ; Nature, vi. p. 444. 
Insects as food : 3 species of Grasshoppers, larvae of Euphaga Jlorifera^ 
H.-S. {Lep.), and of a Melolonthid beetle, and pupae of Borocera cajani, 
Vinson {Lep.), are eaten by natives of Madagascar. Aug. Vinson, ' Voyage 
a Madagascar au couronnement de Radama II.' Paris : 1865, roy. 8vo, 
p. 309. 
For coiTespondence &c. relative to proposed school of insect-economy, cf. 
SB. z.-b. Wien, xxii. p. 60 et seq. 
