Bulletin . neath the surface of the ground. Butterflies,when at rest, hold the wings in a vertical position ; theirantenna? are enlarged toward the extremity, forming a club;they fly in the da^vtime ; and the larv?o form naked chrysalids,never spinning cocoons. Consult Fig. 2. NUMBERS. The number of species of moths in the United States isabout six thousand, while the number of species of butter-flies is less than seven hundred. These numbers representapproximately the number of known species, and while new species are being added tothe list from time to time,it is not likely that thesenumbers
Bulletin . neath the surface of the ground. Butterflies,when at rest, hold the wings in a vertical position ; theirantenna? are enlarged toward the extremity, forming a club;they fly in the da^vtime ; and the larv?o form naked chrysalids,never spinning cocoons. Consult Fig. 2. NUMBERS. The number of species of moths in the United States isabout six thousand, while the number of species of butter-flies is less than seven hundred. These numbers representapproximately the number of known species, and while new species are being added tothe list from time to time,it is not likely that thesenumbers will be greath in-creased. In number of in-dividuals, the lepidopteraare countless. Nature stu-dents need have no fears thatthe svipply will ever becomeexhausted. Allowing thatthe average nimiber of eggslaid by each female is fivehundred, if only one hun-dred of these reached theimago (adult) state, this\y alone would account for Figr. 2. their vast numbers. Many YenoTs^ar Moth. specics, howcver, have from. -10- two to several broods in a season. This accounts for the factthat individuals of many species mav be very scarce in thespring-time, but exceedingly abundant in the autumn, and sug-gests that the best time to collect manv forms is in Augustand September. There are natural causes, however, whichmaterialh lessen the number of individuals. Many are de-stro_ved by birds and beetles ; an incredible number succumb,especially in the larval state, to insect parasites andfung^ousdiseases; but, probably, the most serious ag^enc} in decima-ting their numbers is climatic conditions. A drouth causes ascarcity of food plant and is unfavorable to the man} trans-formations required to accomplish their considerations afford an explanation of the strangephenomenon that a species may be exceeding-h abundant inone 3ear, but unusualh scarce in another. Man} species seemto g-o through a cycle of increase and decrease. There is ag-radual increase in numbers under favorable
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