126 INSECT TRANSFORMATIONS. 



Doors in eggs for the escape, of the larvae. 



a, egg of the louse (Ft icu/us humamts). 6, egg of the pentato- 

 ma. c, shell of a moth's egg found upon the dew-berry, all mag- 

 nified. 



ed with a convex lid, but with a lever of a horny tex- 

 ture, and in the form of a cross-bow, for opening it, 

 the handle being fixed to the lower part of the egg by 

 a membrane, and the bow part to the lid.* On the 

 leaf of a dew-berry (Rnbus ccesius) we found a beau- 

 tifully ribbed egg of some moth, which, having been 

 brought into our study in January, 1830, was hatch- 

 ed by the warmth, and exhibited an opening similar 

 to the elastic cocoon of the emperor-moth; each of 

 the ribs having expanded to allow of the escape of the 

 caterpillar. 



The period at which the eggs of insects are hatch- 

 ed atter deposition depends mainly upon temperature; 

 for by keeping them in an ice-house in summer, the 

 hatching may be retarded, | as it may be hastened 

 (witness the instance in the preceding paragraph) by 

 heat in winter; but there are many other circumstan- 

 ces unknown to us which often hasten or retard the 

 process. The eggs of the blow-fly (Musca vomito- 

 ria) are said to hatch within two hours, J while those 

 of several moths, and numerous other insects, remain 

 unhatched for six or nine months; perhaps, in some 

 cases, even for one or more years. It is worthy of 



* Kirby an4 Spence, iii, 104. t Reaumur, Mem. 



Nouv. Diet. d'Hist. Nat. xii, 564. 



