250 



PSYCHE. 



September, 1901] 



cellular layers and forming veins within 

 the cup or cavity formed by the perip- 

 odal membrane. To assume its normal 

 definitive position in the imago it is only 

 necessary that it be thrust out through 

 the narrow opening, the mouth of the 

 original invagination of the skin hypo- 

 derm. This evagination or shifting 

 from apparently inside the body to out- 

 side occurs at the time of pupation, the 

 wing thereafter lying folded on the 

 ventral thoracic aspect of the pupa. 



References. 



Students undertaking the study of 

 the development of the histoblasts will 

 need to refer to detailed accounts of 

 such development as studied and de- 

 scribed by reputable entomologists (and 

 zoologists). For an introduction to, or 

 general abstract of our knowledge of 

 this subject (up to 1897) see " The 

 Imaginal Discs of Insects," by H. S. 

 Pratt, Psyche, Feb. 1897, vol. 8, no. 250 ; 

 for a detailed account of the develop- 

 ment of the wing discs of a particular 

 insect species see " The Development 

 of the Wings in the Lepidoptera '' by 

 W. F. Mercer, Jour. N. Y. Ent. Soc, 

 March 1900, vol. 8, no. i. For further 



references see the bibliography given 

 in these two papers. 



Histoblasts Showing Externally. 



The integument of the larva of Holo- 

 nisia is too opaque to permit the buds 

 to be visible from the outside of the 

 body, and this is the case with most 

 larvae. But in some the thoracic buds 

 may be readily seen from the outside, 

 and the gross details of their develop- 

 ment followed by simple examination of 

 the exterior of the larvae. This is true 

 for example of the larvae of Cliironoinus 

 (fig. I, B) and especially of Simulium 

 (fig. I, A). The position and gross 

 appearance of the thoracic buds in 

 SiiHii/ium can be seen in young larvae 

 and the growth and the foldings and 

 convolutions of the hypodermal layer 

 followed by examination of successively 

 older larvae. As the larvae of both 

 Simulium and Chirouomus are common 

 all over the country, (CJtironomus in 

 ponds and still pools of streams, and 

 Simulium in clear swift water in dense 

 patches on submerged rocks) some 

 acquaintance at least with imaginal buds 

 can be made without either dissection 

 or sectioning. 



LIFE HISTORIES OF NORTH AMERICAN GEOMETRIDAE.— XXV. 



BY HARRISON G. DYAR, WASHINGTON, D. C. 



Cingiliu cateiiayia Craiii. The mature Eggs. Laid loosely and falling to the 



larva has been described by Harris, Packard, ground. Elliptical, gently flattened on two 

 Coquillett and Scudder. sides, one end distinctly and sharply trun- 



