126 INSECT TRANSFORMATIONS. 



a h c 



Doors in eg^'s for the escape, of Ihe larviB. 

 a, egg of tlie louse (I'c ku/m humanus). b, egg ol the peiitato- 

 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 [Ritbtis ccesius) we found a beau- 

 tifully ribbed egg of some motli, 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 alter 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 romito- 

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

 of several moths, and numerous other insects, remain 

 unhatchcd for six or nine months; perhaps, in some 

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



* Kirby and Spence, iii, 104. t IJ^'aumur, Mem. 



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



