Fig. 36. Cases of the 

 bagworm, Thyridopteryx 

 ephemeraefor mis H a - 



worth. 



HOW TO KNOW THE IMMATURE INSECTS 



etable fragments, etc., these larval cases 

 functioning as cocoons. In these instances 

 the substances are held together by means 

 of a warp of silk and worked up to form 

 cocoons. A large number of other insects, 

 including some of the Neuroptera and Tri- 

 choptera, many Lepidoptera and Hymenop- 

 tera and the Siphonaptera, utilize silk 

 alone in making their cocoons. Among 

 the Tenthredinidae, cocoons of a parch- 

 ment-like or shell-like consistency are fre- 

 quent: in some cases the outer cocoon en- 

 closes an inner one of more delicate tex- 

 ture which may be called a double cocoon. The naked pupae of but- 

 terflies are suspended by silk on the cremaster at the caudal end of 

 the abdomen. In the Diptera (Cyclorrhapha), in- 

 stead of spinning a silken cocoon or constructing 

 a case of extraneous material, the larva prac- 

 tices an interesting economy by retaining about 

 itself one of its own cast, dry skins to form a 

 case called a puparium. This next-to-the-last lar- 

 val skin is not discarded at the time of pupation 

 but is retained until the adult breaks out of the 

 pupal skin. 



Fig. 37. A butterfly pupa. 



WHERE TO COLLECT IMMATURE INSECTS 



Insects are so highly diversified in their food and ways of living 

 that one may find at least a few insects almost any where he looks. 

 When we consider their habits the insects fall into groups which may 

 be rather definitely located. 



A. CHARACTERIZED HABITATS: 

 1. Aquatic Insects. — Those insects that dwell in water or are more or 

 less closely related with water are said to be aquatic. About five per 

 cent of all the insects are aquatic and still another three per cent are 

 closely related with water. In a strict sense,* the truly aquatic insects 

 are those which employ gills to separate the oxygen from the water in 

 which they live. Other insects "obtain their oxygen from the air but 

 because they are closely related with water are said to be semiaquatic 

 insects. If we take a count of the insect orders, almost half of them 

 have aquatic or semiaquatic species. The Ephemeroptera, Odonata, 

 Plecoptera and Trichoptera, with rare exceptions, are strictly aquatic. 



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