436 SUMMARY OF CURRENT RESEARCHES RELATING TO 



night. The investigator believes that the chrysalids can utilise carbon 

 dioxide as green plants do, but one may be pardoned for desiring con- 

 firmation before accepting this momentous conclusion. 



Mechanism of Compound Eye.* — E. J. Spitta suggests that the 

 multiple images produced by the insect's eye are due to pin-hole effects. 

 " It would seem that if the facets of the cornea were considered as 

 nothing but little holes — filled, it may be, with some non-refractive 

 material — all the difficulties about the focusing arrangement are at 

 once swept away ; for it is well known that every image is to a more or 

 less degree in focus with a pin-hole. This would seem to imply that a 

 very perfectly defined image is afforded by the insect's compound eye." 

 The reason for the variation of the diameters of the facets is to enable 

 the insect to possess a differential selection of optical arrangements. A 

 criticism is made of Exner's experiment of photographing through an 

 insect's eye from which retina and pigment were removed, and the eye- 

 cavity filled with glycerin and water — thus making a lens. " It may 

 be said that the photograph was obtained in spite of the cornea being 

 present." 



Palasozoic Insects.f — Anton Handlirsch has made a study of the 

 North American Carboniferous and Permian insects in the U.S. National 

 Museum, and gives a revision of all previously described species, 345 

 (137 re-named or new) in 169 genera (109 new). There is a striking 

 agreement with European forms. Only one order (Blattoidea) extends 

 into the Mesozoic ; all the other orders are replaced in the younger 

 formations by more specialised types. The Palasodictyoptera, which 

 Handlirsch considers the stem group of all winged insects, appear first 

 and decrease from the oldest beds to the younger, while the connecting 

 links or transitional groups between the Palaeodictyoptera and modern 

 insect groups appear later than their conjectural ancestors, attain their 

 maximum in the middle beds, and with the close of the Palasozoic 

 again vanish. 



Influence of Temperature on Lepidoptera.J — H. Federley has made 

 many experiments on the influence of changed temperature on the 

 markings and coloration of Heterocera. Thus, low temperature favours 

 black pigments, e.g. in Saturma pavonia • warmth changes the grey 

 markings of Lymantria dispar $ into brown, and so on. The scales are 

 very modifiable in shape, size, and number. Of this many illustrations 

 are given. According to the author, the thermal influence operates in 

 part by altering the pressure of the hasrnolymph ; in part, perhaps, by 

 directly affecting the metabolism in the plasma of the scale mother-cells. 



Effect of Temperature on Insect Developments — F. Merrifield 

 discusses this subject, illustrating his conclusions by reference to various 

 experiments. There appear to be various degrees of response to changes 

 in temperature ; some species react with great regularity, on others 



* Journ. Quekett Micr. Club., 1906, pp. 263-8. 

 t Proc. U.S. Nat. Museum, xxix. (1906) pp. 661-820. 



% Festschrift fur Palmen, No. 16 (Helsinfors, 1905) pp. 1-118 (3 pis. and 7 figs.). 

 See also Zool. Zentralbl., xiii. (1906) pp. 329-31. 



§ Trans. Entomol. Soc, 1905, pt. 5, pp. lxxxiii.-cxi. 



