154 



THE AMERICAN- ENTOMOLOGIST. 



to the differences in the mode of breeding 

 adopted by each of tliese three parties; and that 

 Dr. Fitcli's four different species of Joint-worm 

 Flies are not true species, but mere varieties, so 

 far at least as can be established from their 

 colorational differences. 



Unity of Habits in Insects and other Animals. 



If we consider for a moment the habits of the 

 larger animals, with which most of us are better 

 acquainted than with those of insects, we shall 

 find that the same genus of animals always has 

 the same general habits. For example, the 

 species of the Horse genus — the Horse, the 

 Quagga, the two species of Zebra, and two 

 or more species of wild Ass — all of them feed 

 upon herbage, live in the plain and not in the 

 foi'est, feed in the day time and not in the night, 

 gather together in large herds led by the old 

 males, and when attacked defend themselves 

 by the hoofs of their hind legs. On the other 

 hand, the multifarious species of the Cat 

 genus — the Lion, the Bengal Tiger, the various 

 Leopards and Panthers of the Old World, and 

 the Puma (Couguar) and Panther (Jaguar) of 

 the New World — all of them feed upon flesh, 

 haunt the forest rather than the plain, seek for 

 their prey in the night rather than in the day- 

 time, never gather together in herds but live 

 either solitary or in pairs, and fight with their 

 mouths and their front paws rather than with 

 their hind paws. Look where we will among the 

 larger animals, whether among the Bear genus, 

 the Dog genus, the Owl genus, the Hawk genus, 

 the Pigeon genus, or the Sparrow genus, we 

 shall find the same law to hold good. And 

 the reason of it, upon a little consideration, be- 

 comes at once manifest to our minds. Different 

 species are classified under the same genus, be- 

 cause they have very nearly the same structure. 

 Now, it is the structure that determines what 

 the habits of the species are to be. For exam- 

 ple, a bird with a hooked bill like that of an 

 Eagle is necessarily debarred from pecking 

 vegetable food like a Sparrow, and is compelled 

 b)' that and the other corresponding parts of its 

 organizatipn to live by tearing and rending 

 living animals. Conversely, a Sparrow is 

 physically incapacitated from preying upon 

 animals of its own size, as does the Eagle, and 

 is driven b)' its structural peculiarities to peck 

 at small insects, fruits and seeds. Conse- 

 quently, as the Genus and the Habits of any 

 particular species of animal are both of them 

 determined by the Structure, when the Genus 

 of two species is the same, the Habits also must 

 of necessity be the same or very nearly the same. 



To this great and universal law has been given 

 the name of the Unity of Habits ; and it may be 

 recognized everywhere, not only among the 

 liigher animals, but also among Insects. 



Prof. Agassiz has used language which would 

 seem to imply that he extends to a certain de- 

 gree the operation of this law, not only to all the 

 species belonging to the same genus, but also 

 to all the genera belonging to the same Family. 

 " The more I learn upon this subject," he says, 

 "the more am I struck with the similai'ity in 

 the verj' movements, the General Habits, and 

 even the intonation of the voices of animals, 

 belonging to the same Family."* But there 

 are several cases among the higher animals, 

 where genera classified by all authors in the same 

 Family have very widely distinct habits ; and we 

 find mau)-^ such examples among the great Class 

 of Insects. For instance, most of the multi- 

 farious genera of the Ground-beetles {Carabus 

 family) are cannibals and prey upon other in- 

 sects ; but there is a particular genus of them 

 {Zahrus) , found in Europe but not in America, 

 which feeds upon living and growing vegeta- 

 bles. Again, most genera of the above-named 

 Family of Beetles are terrestrial in their habits ; 

 but there is a particular genus of them (Oiides) .j 

 which habitually in the perfect beetle state 

 lives under water, and when endeavoring to 

 escape generally makes for the water, and 

 as soon as it has reached it immediately 

 crawls under any floating rubbish and disap- 

 pears from view.t Lastly, the genera Arma . 

 and Stiretrus (Fig. 41 , p . 46 and fig. 43, p. 47 of the 

 Amek. Entom.), both of which have very stout 

 robust beaks suitable for i^iercing the bodies of 

 other insects, are cannibal in their habits, as wc 

 showed in the pages just now referred to; 

 while all the genera of the same group {Scutel- 

 lera family) of the True Bugs {Heteroptera) , 

 which have slender beaks adapted only for 

 piercing vegetation, are almost exclusively veg- 

 etable-feeders. 



The law then, as we assume it to exist, may 

 be briefly stated as follows: In the case of all 

 known animals, species belonging to the same 

 genus have the same, or nearly the same habits ; 

 and this is also partially true of genera belong- 

 ing to the same Family; but not unfrequently 

 genera belonging to the same Family have very 

 widely distinct habits. 



*EsHay on Classification, p. 59. 



tFor the habits of Oodes Jluvialis Loo., see a Paper by the 

 Senior Editor in Pioc. Ent. Soc. Phil. Ill p. 643. We have 

 kept this insect in an aquarium and know the facts to be as 

 stated. Mr. H. Hike, of Washington, D. C. , has since in- 

 formed us that he has detected the same habits in Oodes 

 amaroides Dejenu. 



