334 MODERN CLASSIFICATION OF INSECTS. 
beautiful eyes or spots. The Fritillaries are fulvous, varied on the 
under side with pearly patches. Various species of butterflies are re- 
markable for their periodical or irregular appearance: of these the 
species of Colias, or clouded yellows, as they_are termed by collectors, 
Cynthia Cardui and Vanessa Antiopa, are pre-eminent ; thus the last- 
named insect, according to Mr. Haworth (Lep. Brit. p. 28.), will not 
be seen for eight, ten, or more years, and then appear as plentiful as 
before ; indeed, about seventy years ago, it suddenly occurred in such 
profusion as to obtain the name of the Grand Surprise from the 
Aurelians of that day. Mr. Haworth conjectures this may be owing 
to the eggs having, like the seeds of plants, lain dormant, not hatching 
until some extraordinary but undiscovered coincidences awake them 
into active life; others attribute it to the failure of their natural 
enemies, as the Ichneumons and soft-billed birds, and others to an 
increased temperature. But these are mere conjectures, and seem 
to want confirmation from the circumstance noticed by Stephens 
(Illustr. Haust. vol.i. p.10.); that Cynthia Cardui, although pe- 
riodical in some places (“occurring every third or fourth year most 
copiously, and breeding even in the metropolis itself;” Stephens, 
vol. i. p.48.), appears constantly in others; and see Bree, in Mag. 
Nat. Hist. No. 39. 
The majority of these insects are but short-lived, but certain indi- 
viduals of some species survive the winter, passing that period of the 
year in a state of lethargy. It has been generally supposed that these 
(which chiefly belong to the g nus Vanessa) were females which had 
been produced late in the preceding autumn, and which, although 
impregnated at that time, had delayed the act of oviposition until the 
renewal of the season brings forth a fresh supply of food for their 
offspring. M. Boisduval, however, opposes this, stating that these 
individuals had undergone a state of lethargy from a much earlier 
period (having observed Vanessa Polychloros and Urtica in this state 
in August), and that their impregnation had not taken place until the 
following spring.* Mr. Stephens states that both sexes of Gonepte- 
ryx Rhamni hybernate. Other species appear to be double-brooded 
in the course of the year (Papilio Machaon, Gonepteryx Rhamni, 
&c.); some of these, however, in certain seasons, seem only to be 
single-brooded (as Polyommatus Argiolus). 
* See hereon Brown, in Mag. Nat. Hist. No. 39., and Bree contra, in ditto, 
No. 42. 
