250 JOIRNAL OF ECONOMIC ENTOMOLOGY [Vol. 4 



tivel}' by nuiiil)ers. The colored catch cards bear the head, and its 

 initial numbers, as: — 247, — 248, citrus fruits. 



Under each head numbers are multiplied as follows: A head with 

 numbers 247, 248, follows these numbers with 1,247, 1,248, 2,247, 

 2,248, 3,247, 3,248, etc. Thus a head with two numbers admits of 

 two hundred species being placed under it before the numbers reach 

 the six-figure space. In all cases the final numbers are the same for 

 a head. 



The system, as so far outlined, applies only to insects that are found 

 on their respective food-plants, and to those falling under the non- 

 plant heads adopted. 



All enemies, whether parasites or predatory insects, of the species 

 under the above heads, are designated by adding to the host-number 

 the following: 



°a — Egg-parasites. 

 °2a — Dipterous entoparasites of any stage. 

 °3a — Hymenopterous entoparasites of any stage. 

 °4a — Heteropterous predators of any stage. 

 °5a — Coleopterous predators of ditto. 

 °6a — Lepidopterous predators. 

 °7a — Dipterous predators. 

 °8a — Neuropterous predators. 

 °9a — Hymenopterous predators. 

 °10a — Acarid ectoparasites or predators. 



Other enemy heads can be added for stylopid or other entoparasites^ 

 and for other predators or ectoparasites, etc. The letters of the English 

 alphabet are to be used, and then doubled, tripled, etc., if required; 

 as 247°3a to 247°3z, 247°3a2 to 247°3z2, 247°3a3 to 247°3z3, etc., 

 variations as preferred may be adopted. 



Hyperparasites, etc., can be numbered with a repetition of the 

 above enemy suffixes added to the host-number; as 247°2a° 3a to 

 247°2a °3z, etc. 



I have used the suffix °20 (a to z, etc.) for fungous diseases; others 

 can be added for bacterial diseases, etc. 



It will be seen that this system is highly elastic, and can be used 

 at once before the names of any of the species of insects are known. 

 Only the names of the plants are needed. 



An index of the heads is kept separate, for the purpose of readily 

 finding the numbers belonging to each. 



With any other system the greatest confusion exists until the species 

 of insects are known by name. With this system,, order is maintained 

 throughout, as well as a food plant catalog of the species. 



