Apbil 1, 1887.] 



SCIENCE. 



319 



uians a group of about one himdred species, all with 

 different habits, — the Eupithecia, studied for many 

 years by M. Goossens of Paris, from whom these de- 

 tails are taken. The E. rectangularia, so named from 

 the design of the upper wings, emerges from the 

 pupa at Paris in April. After pairing, the female 

 deposits an egg in the midst of the flower of an 

 :apple, pear, or quince tree. The egg, which is j'^el- 

 low, is well hidden in the heart of the flower, and is 

 hatched in a fcAV days. The larva, hardly visible to 

 the naked eye, is of a rosy-white color, and begins 

 its work by attaching one end of a thread to the top 

 of a petal, and the other to the heart of the flower ; 

 "by its traction the petal being bent down. The same 

 is done with the five petals ; and the larva is thus 

 enclosed, protected from wind, rain, and jDarasites. 

 It can Avith impunity devour the base of the flower 

 and of the petals. The pollen of the male flower 

 cannot fecundate the female flower, which is the one 

 selected by the larva, and consequently there is no 

 reprodiiction and no fruit. As the eggs have been 

 widely scattered by the female's instinct, a few of 

 these insects may render abortive the flowers of an 

 orchard, or even of a region, without any reasonable 

 explanation for the horticulturist. So many similar 

 insects attack in this or other ways our fruit-trees, 

 that in some places it is an astonishing event to see 

 an apple on a tree. 



While remembering that the European sparrows 

 have done great service to New York by destroying 

 the larvae of the geometers, or canker-worms, almost 

 all of which are bare and smooth, it must be said 

 that they are useless, and even injurious, in presence 

 of the larvae of Orgyia. Sparrows, like most birds 

 of the genus, do not like the hairy larvae, from the 

 irritation they cause in the throat and stomach. One 

 may frequently see poultry seize such larvae, kill 

 them by beating them on the ground, and then leave 

 them without eating them. 



Bombycidae. — In this family belongs the larva 

 which of late years has been so destructive in the 

 parks and gardens of New York. For a long time 

 we sought to discover its place of origin, how it ar- 

 rived here, became acclimated, and multiplied to 

 such an astonishing degree without meeting the 

 parasite which destroys it. At first we thought it 

 had been imported from France, where a species of 

 the group, Orgyia antiqua, had been known in the 

 Paris squares for several years, devouring trees and 

 shrubs, and sometimes a pest among the rose-bushes. 

 After having carefully compared it, with the aid of 

 M. Goossens of Paris, it seemed to come very near 

 to, if not to be, the 0. vetusta, — a species common 

 in California, which places its cocoons in the inter- 

 stices of the bark of trees, the grooves of lamp-posts, 

 cracks in wooden fences, and also between the hoops 

 on wine-casks on the wharves. In the last way, the 

 insect, which does not bear transportation well, might 

 be carried even across the continent or the ocean. 

 Without the necessity of this derivation, it has now 

 been ascertained that the species is O. leucostigma 

 Smith, which occurs in the neighborhood of Daven- 

 port, lo. (see Proceedings of the Academy of natural 

 sciences, 1867-78, Davenport, lo., vol. i. p. 177). 

 This may be found much nearer. 



It is precisely at its youngest age that the life of 

 the insect is best protected. An egg, according to 

 Eeaumur and others, will endure a cold of 50° be- 

 low freezing, and the boiling-point of water in heat, 

 Avithout losing its vitality. In this age there being 



no means of defence or escape, a species would soon 

 be destroyed without these natural means of resist- 

 ance. After hatching, the larvae are dispersed, and 

 conceal themselves in places resembling them in 

 color, until the survival of the species is assured. 

 Nature always furnishes eflicient protection when 

 most needed. 



Before taking up the Orgyia larva, we wish to 

 speak of a parasite which we discovered, — an inof- 

 fensive dipterous insect, all of whose metamorphoses 

 we have studied, which would soon destroy the 

 larvae, if the sparrows, in their turn, did not become 

 the persistent and greedy devourers of said parasite. 



At the two seasons of the year when the larva 

 makes its ap^Dcarance in New York, this dipterous in- 

 sect is on the watch, and as it crawls along the 

 ground deposits an egg in the midst of its hairy cov- 

 ering. Toward the end of winter or beginning of 

 spring the dipterous larva is developed at the expense 

 of the Orgyia pupa. Then, instead of a moth being 

 hatched, appears an active fly with extended wings, 

 large enough to be observed by the naked eye. Pre- 

 cisely at this moment the sparrows hunt them, de- 

 vouring great numbers, which, if allowed to multiply 

 by this strange manner of hatching, would soon 

 much reduce the number of the Orgyia, if they did 

 not completely destroy the species. Here comes in 

 the reflection that the sparrows are now not only 

 useless, but actually aid in the multiplication of the 

 destructive Orgyia. 



But not to completely ostracise these noisy and 

 vivacious strangers from the land where, with so 

 many of my countrymen, they have been so hospit- 

 ably received, let them remain as long as the people 

 care to protect them ; inasmuch as, without disturb- 

 ing them in their picturesque dwellings, there is a 

 way of destroying the Orgyia, bj^ an anodyne and 

 easy process, doing no harm either to plants or ani- 

 mals, nor to the visitors of the beautiful parks of the 

 city. Nothing is more disagreeable to the fair prom- 

 enaders than to feel upon the neck, see suspended 

 from their head-dress or hair, or crawling over their 

 dresses, these little creatures, interesting to the scien- 

 tific observer, but causing a shudder to them. 



The larvae of Orgyia know well the laws of aero- 

 station, and the use of the parachute. M. CajDi'onnier 

 of Belgium, a few years ago, in the month of Octo- 

 ber, made this singular observation on the method of 

 their dispersion. It must be remembered that the 

 females of Orgyia are wingless, — a character which 

 distinguishes them from the genus Liparis, in which 

 the females have wings. The question was asked 

 how the Orgyia could gain access to an enclosure 

 newly cultivated. M. Capronnier replied that he 

 had seen the small larvae emerge from eggs laid in 

 the cocoon of Orgyia. They made a thread from 

 which they suspended themselves free in the air, when 

 the wind carried off the larvae with the thread, no 

 doubt to great distances, and they very soon disap- 

 peared. This mode of dispersion is similar to that 

 observed in some spiders. 



The genus Orgyia was established by Ochsen- 

 heimer, and belongs to the Bombycidae, or those 

 whose larvae make cocoons from their own hairs, or 

 particles of earth hardened by a salivary secretion, 

 etc. The adults are of small size. The males, of 

 rich colors usually, fly rapidly in full sunlight ; the 

 antennae wide, bipectinated, doubtless with an acute 

 sense of smell, which guides them to the females. 

 The last are five or six times as large as the males, 



