THE AMEEICAN ENTOMOLOGIST. 



45 



{Carpocapsa 2)omonella, Limi.)* Thinking that 

 it might be possible tliat, although tlie bogus 

 Colorado Potato-bug has for about halfa century 

 refused to feed upon the potato in a state of 

 nature, it might yet be compelled by starvation 

 to feed upon that plant in a state of confinement, 

 we placed two of the larvae received from Mrs. 

 Freeman in a vessel along with some potato 

 leaves; but, instead of feeding voraciouslj^ upon 

 them, as the larvae of the true Potato-bug would 

 certainly have done, they only nibbled a few 

 small lioles in them about the size of a pin's 

 head, and then in a week's time died of starva- 

 tion. This, however, can scarcely be quoted as 

 a decisive experiment, because these larvas had 

 fasted for about a day before they reached us, 

 owing to the leaves in which they were packed 

 having dried up ; and because no vegetable- 

 feeding animals can stand long fasting as well as 

 flesh-feeding animals do. But even if they had 

 actually fed upon potato leaves quite freely in a 

 state of confinement, it by no means follows that 

 the mother Beetle would deposit her eggs upon 

 the potato in a state of nature, and thereby com- 

 pel her future progeny to feed upon that plant. 

 That she will do so upon her natural food-plant, 

 the horse-nettle, we know ; and, according to 

 Mr. "Walter of Alabamj, she will also do so upon 

 the egg-plant, which is thorny like the horse- 

 nettle. But apparently she is naturally indis- 

 posed to go one step further, and lay her eggs 

 upon a smooth species of the same botanical 

 genus, namely the potato. 



We have exxDerimentally ascertained that 

 neither ducks, geese, turkeys nor barndoor fowls 

 will touch the larva of the Colorado Potato-bug 

 when it is offered to them ; and there are numer- 

 ous authentic cases on record, where persons 

 who have scalded to death quantities of these 

 larvae, and inhaled the fumes from their bodies, 

 have been taken seriously ill, and even been 

 confined to their beds for many days in conse- 

 quence. Still, these larvas are not near so 

 poisonous as the old fashioned Blister-beetles 

 already referred to as infesting the potato ; for 

 these last are, even in small doses, one of the 

 most powerful medicines, and therefore in larger 

 quantities one of the most virulent poisons 

 known to the medical profession. 



Foes of the Colorado Potato-bng. 

 Persons not famiUar with the economy of in- 

 sects are continually broaching the idea that, 

 because the Colorado Potato-bug is in certain 



• See on this subject the First Annual Report on the Noxious 

 Insects of niinois, by Benj. D . Walsh, pp . 29-30, in the Trans- 

 actions of the Illinois State Horticultural Society for 1807. 



seasons comparatively quite scarce, therefore it 

 is about to disappear and trouble them no more. 

 This is a very tiillacious mode of reasoning. 

 There are many insects — for instance, the no- 

 torious Army-worm of the North (Leuccmta 

 imipuncta, Ilaworth) — which only ajjpear in 

 noticeable numbers in particular j-cars, though 

 there arc enough of them, left over from the crop 

 of every year to keep up the breed for the suc- 

 ceeding year. There are other insects — for in- 

 stance the Cankerworm {Anisopteryx vernatu, 

 Peck) — which ordinarily occur in about the 

 same numbers for a series of years, and then, in 

 a particular season and in a particular locality, 

 seem to be all at once swept from off the face of 

 the earth. These phenomena are due to several 

 different causes, but principally to the variation 

 and irregularity in the action of cannibal and 

 parasitic insects. We are apt to forget that the 

 sj'stein of Nature is a very complicated one — 

 parasite preying upon parasite, cannibal upon 

 cannibal, parasite upon cannibal, and cannibal 

 upon parasite — till there are often so many links 

 in tlie chain that an occasional irregularity be- 

 comes almost inevitable. Every collector of 

 insects knows, that scarcely a single season 

 elapses iu wliich several insects, that are or- 

 dinarilj' quite rare, are not met with in pro- 

 digious abundance ; and tliis remark applies, not 

 only to the plant-feeding species, but also to the 

 cannibals 'and the parasites. Now, it must be 

 quite evidciit that if, in a particular season, the 

 enemies of a particular plant-feeder are unusu- 

 ally abundant the plant-feeder will be greatly 

 diminished iu numbers, and will not be able to 

 expand to its ordinary proportions until the 

 check that has hitherto controlled it is weakened 

 in force. The same rule will hold with the ene- 

 mies that prej^ upon the plant-feeder, and also 

 with the eueniies that prey upon those enemies, 

 and so on ad injinitum. The real wonder is, 

 not that there should be occasional irregularities 

 in the numbers of particular species of in- 

 sects from year to year, but that upon the whole 

 the scheme of creation should be so admirably 

 dove-tailed and fitted together, that tens of 

 thousands of distinct species of animals and 

 plants are able permanently to hold their ground, 

 year after year, upon a tract of land no larger 

 than an ordinary State. 



To afford some practical idea of the number 

 of enemies that often prey upon a single insect, 

 wo will now give a brief account, illustrated by 

 figures, of a few of the various cannibal insects 

 that attack the Colorado Potato-bug, either in 

 the egg, larva or perfect state. The list might 

 be easilv swelled to over a score, but to avoid 



