ZOOLOGY AND BOTANY. MICROSCOPY. ETC. 633 



a, Insecta. 



Insects supposed to be distasteful to Birds.* — Mr. A. G. Butler, 

 "wlio keeps a large number of birds, has observed that no insect in any 

 stage was ever refused by all tbe birds ; what one bird refused, another 

 would eat. He is of opinion that metallic colours are not a source of 

 protection to birds ; a bird knows nothing of the nature of metal, but 

 whatever is brilliant and shining he makes for at once to see whether it 

 is good to eat. It appears to him that certain species of Lepidoptera 

 and of other insects may become abundant in certain years owing to 

 the temporary scarcity of their particular enemies, but they never enjoy 

 perfect immunity from destruction. The spider-like appearance of the 

 larva of Staurojnis is not a protection against birds, for, if there is any- 

 thing that all insectivorous birds love it is a spider. The sting-like 

 tentacles of the larva of Dicranura vinula are likewise no protection ; 

 three young nightingales never hesitated for a moment to use the 

 tentacles as handles to assist them in knocking the life out of the cater- 

 pillar before devouring it. 



Histology of Insects.f — Dr. C. Schaffer first treats of the ventral 

 glands in the larvaB of Lepidoptera. As seen in Hyponomeida evoivj- 

 meJla the ventral gland is a tube which commences in the metathorax, 

 which is continued forward to the anterior edge of the prothorax where 

 it opens on a conical projection which is provided with two retractors. 

 It is surroiinded by a rich system of trachete arising from several large 

 trunks. It is distinctly divisible into an anterior and a posterior 

 portion. A similar organ is found in Harpijia and in Plusia gamma, 

 and it may, tlierefore, be reasonably supposed to be widely distributed 

 among the Lepidoptera. It appears to be derived from a simple 

 invagination of the hypodermis. 



The second subject dealt with is the site of blood-formation in the 

 larvfe of Insects ; in Hyponomeuta evonymella the blood is found in 

 the fat-body (in its widest sense) and in the matrix of the tracheae. 



In SmerintJius, Ocneria, Gasiropacha, Pieris, Vanessa, and Haipyia, 

 the cells which form the blood-forming tissue are differentiated during 

 the embryonic development of the fat-body. In Lyda erythrocepJiala the 

 site of origin of the blood is widely distributed through the body ; while 

 in Hyponomeuta the tissue is only found at the rudiments of the wings, 

 it has in Lyda the form of cell-aggregates which are scattered through 

 the wholef thorax and abdomen of the caterpillar, though always in 

 more or less close connection with the fat-body. In the larvae of Musca 

 the fat-body is chiefly formed from the tracheal matrix, while the 

 hypodermis gives rise both to blood-corpuscles and to cells of the fat- 

 body ; the latter possibly give rise to the fat-body of the adult. 



The chief point brought out by the author is the genetic connection 

 between the fat-body and the blood corpuscles in the fii'st place, and then 

 of the ectoderm (hypodermis and tracheal matrix) on the other side, and 

 the fat-body and blood corpuscles on the other. Tlie last may, in the 

 nomenclature of v. Wielowiejski, be called the blood-tissue. The chief 

 function of the fat-body is to take uj) and give out again nutrient sub- 

 stances, so that the proposed name is physiologically as well as morpho- 



* Ann. Hnd Mag. Nat. Hist., iv. (1889) pp. 171-3. 

 t Zool Jahrb. (Abth. f. Anat.), iii. (1889) pp. 611-?2 (2 pis.). 

 1889. 2 Y 



