344 



ELEMENTARY ENTOMOLOGY 



collection look better, but also makes it much easier to handle and 

 study. The general rule followed by entomologists is that one fourth 

 of the pin shall project above the insect. For this purpose a pinning 

 block is almost indispensable, the construction of which will be 

 readily understood by referring to Fig. 479. The lower hole should 

 be one fourth the length of the pin in depth, the second, one half 

 the length, and the third, three fourths the length. After the pin 

 has been pushed through the insect, the head is inserted in the 

 lower hole and the insect pushed down until the back touches the 

 block. The second hole is for evening up the labels, and the third 

 one for placing points on the pins. 



A great deal of skill is required in pinning insects properly. 

 The specimen should be grasped by the thumb and forefinger 



FIG. 479. A pinning block 



and held very lightly in the groove formed between the tips of the 

 thumb and forefinger while the pin is inserted in the proper place. 

 Another method is to place the insects on some soft substance, as 

 a folded handkerchief, and turning the insect ventral side down, 

 insert the pin, finishing the operation on the pinning block. 



Since the different groups of insects present certain structural 

 peculiarities, the following system of pinning the members of 

 different orders has gradually been formed. (The directions for 

 mounting on points and slides are given below.) 



Thysanura and Collembola. All of the smaller species are 

 mounted on microscope slides ; the larger forms are pinned through 

 the metathorax. A very fine wire is run entirely through the body, 

 to serve as a support. In the case of the Thysanura, this should 

 be inserted just underneath the long, median setae and run forward 

 well into the thorax. If the end is left projecting, it may be made 

 to serve as a support for the posterior setae. 



