572 INSECTA. 



majority of these insects are covered with a mealy matter, or with cottony threads, sometimes arranged in rows. 

 The larvaj of the Hemerobii, those of many Diptera, and CoccinellK, destroy a great number of plant-Uce. M. 

 Aug-. Duvau has communicated to the Academy of Sciences the interesting- result of his observations on these 

 insects, and his memoir has been inserted in the collection of those of the Museum (fllist. Nat. 



The Aphis of the oak (A. Quercf/s, Linn., R&umur, 3, pi. 28, f. 5), is remarkable for having the proboscis at 

 least three times as long as the entire body. 



M. Blot has published, in the Memoirs of the Linnoean Society of Caen, 1824, various curious observations upon 

 a species found in the Departement du Calvados, -which is very injurious to the apples, destroying the young 

 shoots. He considers it as the type of a new genus, which he calls Myzoxyle. [It is probable that this insect is 

 identical with that so well known in England under the name of Apple-blight, which is covered entirely with a 

 white cottony secretion, and which multiplies in vast numbers in the crevices of the bark of diseased apple-trees.] 

 De Geer also described a species of Aphis found upon the apple, but which differs materially from that described 

 by M. Blot, which last has no horns on the abdomen, the antennae are shorter, and, according to M. Blot, only 

 5-jointed, the second joint being the longest. [The species of this family, Aphids, are extremely numerous, 

 almost every plant possessing a distinct species. They however require a more minute investigation than has yet 

 been given to them. The Senator Van Heyden has described several new genera recently in the Memoirs of the 

 Museum Seckenbergeanum.~\ 



Aleyrodes, Latr. (Tinea, Linn.), has the antennae short, 6-jointed, and the eyes notched. Type, T. proletella, 

 Linn. ; Reaumur, Memoires, vol. ii. pi. 25, fig. 1—7, resembles a small white moth, having a small blackish spot 

 on each wing-cover. It is found on the leaves of the Chelidonium, cabbage, oak, &c. Its larva is oval, very flat- 

 tened, like a minute scale, and resembles that of Psylla. The pupa is fixed, and inclosed in an envelope, so that 

 this insect undergoes a complete metamorphosis. 



THE THIRD FAMILY OF THE HOMOPTEROUS HEMIPTERA,— 



The Gallinsecta, — 



Of which De Geer formed a distinct order, have only a single joint* in the tarsi, with a single hook at 

 the tip. The male is destitute of a proboscis, has only two wings, which shut horizontally upon the 

 body ; the abdomen is terminated by two threads. The female is without M'ings, and 

 furnished with a proboscis. The antenna are filiform, or thread-like, and often eleven- 

 jointed (nine in the species described by Dalman in the memoir noticed below). These 

 insects compose the genus 



Fig. 101.— Coccus Coccus, Linn, (or Scale-insects). 



acens, male & ' \ / 



female. fj^g jj^rk of many of our trees appears often warty, by reason of a great number of small 



oval or rounded bodies, like a shield or a scale, which are fixed to them, and in which no external 

 traces of the insect are to be observed. They nevertheless belong to this class of animals, and to the 

 genus Coccus. Some of these are females ; the others are young males, and which are similar to 

 them in form. But a period arrives when all these individuals undergo singular changes. They fix 

 themselves to the plant, the larva; of the males for a determinate period necessary for their trans- 

 formations, and the females permanently. If observed in spring, their bodies are noticed gradually to 

 increase in size, ending in their acquiring the appearance of a gall, being either spherical, kidney- 

 shaped, boat-shaped, &c. The skin in some is entire and very smooth ; in others it is incised, or offers 

 traces of segments. It is in this state that the females are impregnated, shortly after which they 

 deposit their eggs, of which the number is very great ; these tbcy deposit between the ventral surface 

 of their bodies and a layer of a cottony secretion, with which they had previously hned the spot on 

 which they had stationed themselves. Their bodies subsequently dry up and become a solid cocoon, 

 which covers the eggs. Other females envelope their eggs in a very abundant cottony secretion, which 

 equally defends them. Those which are of a spherical form become a kind of l)ox, inclosing the eggs. 

 The young Scale-insects have the body oval, very flat, and furnished with the same organs as their 

 mother. They disperse themselves over the leaves, and reach by the end of the autumn the branches, 

 on which they affix themselves in order to pass the winter. Some, the females, prepare at the com- 

 mencement of summer to become parents ; and the others, or the larvae of the males, are transformed 

 into pupae beneath their own skin. These pupre have the two fore-feet directed forwards, and not 

 backwards, like the four hind legs, and like all the legs of the other inactive pupae. Having acquired 



* Ualinaii, in a memoir upon some species of Cotcus, considers that the number of the joints in the tarsi is three. 



