47 



" The larva sometimes emerges at the micropyle, but there is no rule 

 for this, for it frequently emerges at any other portion of the egg ; 

 indeed, among the Nepticulides it eats its way through the base of 

 the egg into the leaf on which it is laid." * It is possible that the 

 point of emergence selected by the larva is that portion of the shell 

 which is the thinnest. 



Eggs are, broadly speaking, of two kinds — " upright" and ovoid, or 

 so-called "flat." Dr. Chapman first separated the eggs of Lepi- 

 doptera into these two distinct groups : the " upright " egg having the 

 micropyle at the apex, and the micropylar axis perpendicular to the 

 surface on which the egg is laid ; and the ' ' flat " egg with the 

 micropyle at one end of the egg and the micropylar axis parallel to 

 the surface on which the egg is laid. 



Mr. Tutt has used these characters as one of the tests which he 

 applied in formulating his advanced system of classification ; and 

 thus we find in his " British Lepidoptera," Vol. I. (a work I can 

 strongly recommend to any lepidopterist who makes the ova 

 a study), the arrangement of the Lepidoptera under three 

 stirpes or main divisions, two of which are flat-egged stirpes, 

 viz. the Micropterygo-Sphingid and the Eriocranio-Geometrid, 

 and one upright-egged stirps, the Hepialo-Noctuid. By this 

 test many hitherto anomalous positions for certain families 

 were proved to be erroneous, and one finds the Notodonts carried 

 over to the Hepialo-Noctuid stirps in this classification, the Cymato- 

 phorids attached to the Geometrid stirps, whilst the position of 

 many other families may be more or less accurately checked by the 

 peculiar structure of the ova. 



It will be observed that the " upright" eggs have a more elaborate 

 sculpturing than the " flat " eggs, the surface being onamented with 

 longitudinal ribs and transverse bars, whilst the " flat " eggs are 

 usually oval in shape, yellow in colour, often very soft, with a de- 

 pression on the upper surface, and the sculpturing slight and shallow. 

 Some of the lower forms of these latter are devoid of markings, 

 and one is led to believe that they represent in some measure the 

 primeval form of egg. 



At this point it would be interesting to observe the difference in 

 the position of the insect in the act of depositing a flat egg and an 

 upright egg ; one would imagine that in the latter case the egg is 

 deposited when the abdomen is in a position more or less perpen- 

 dicular to the surface on which the egg is laid, whilst in the former 

 case a horizontal position seems to be the more probable, or some 

 structural differences may exist in the ovipositing organs. 



The flat-egged stirpes comprise the following families : — The 

 so-called Micro-Lepidoptera. Geometrids, Anthrocerids, Lachneids 

 (Lasiocampids), Saturniids, Sphingids, etc. 



The upright-egged stirpes :— The Cossids, Notodonts, Noctuids, 

 Liparids, Arctiids, Hesperids, and Papilionids. 



'' " British Lepidoptera," J. W. Tutt, vol. i, p. i6S. 



