CLASSIFICATION OF INSECTS. 7 



lating to insect larvae may be profitably dealt with without taking 

 into account the adult insects. This is particularly true with 

 taxonomic studies, for these, when used with due caution, are 

 very valuable in modifying any conclusions based upon studies 

 of the adults. 



Even the eggs of insects furnish characters which are suitable 

 for taxonomic treatment. Like the later stages, the eggs com- 

 monly show distinctive features in the form and structure of the 

 chitinous shell, aside from the contained embryo. Like the 

 similarly large eggs of birds, they are frequently characteristically 

 colored, although a spotting or color pattern is rather rare among 

 insect eggs. The relation of color development to environment is 

 nicely illustrated by the eggs, as only such as are deposited in 

 places exposed to the light show a color other than that imparted 

 by the whitish or buff-colored yolk. The color often changes 

 where the shell is transparent, as the developing color of the larva 

 is to be seen through the shell. Whether the color of insect eggs 

 may be interpreted on the basis of protective or warning color 

 seems very doubtful. In certain bright yellow or orange eggs, 

 as for example those of many chrysomelid beetles the color may 

 be due to shell color or only to the brightly colored yolk. There 

 seems not to be sufficient uniformity in egg-color, however, to 

 attempt any explanation of its probable function. 



The eggs of Lepidoptera, especially those of the butterflies, 

 have received more attention than those of any other insects. 

 Externally these are commonly of unusually complex sculpture, 

 with surface reticulation or areolation, sometimes assuming the 

 form of longitudinal and transverse ribs. Scudder ('89) has 

 shown the possibility of classifying the eggs of some of our North 

 American butterflies, and Tutt ('05- '06) gives an interesting 

 resume of the egg-structure of some of the groups of British 

 butterflies. According to Tutt, the eggs of the various species 

 of any given family are almost always similar, although varying 

 in detail in the several forms. Thus, the Thymelicid eggs are 

 flat with three axes of different lengths, differing from those of 

 the other groups which are circular in horizontal section. In 

 the Urbicolid skippers they are somewhat more than hemis- 

 pherical; in the Lycsenids shallow, flattened, tiarate or echinoid; 



