76 



a few exceptions. Several dipterous species bring forth their young 

 alive, and the Hippoboscidae, a very singular family of dipterous in- 

 sects,, do not cast their young until they have advanced to the pupal 

 state. The plant lice, which belong to -the homopterous division of 

 the Hemiptera, present a very singular anomaly in their method of 

 reproduction. 



The female perfect insect, having deposited her eggs in the fall, 

 dies; in the spring these eggs hatch, producing only unsexual (or im- 

 perfect female) individuals, wh'ich, arriving at the perfect, or appa- 

 rently perfect, state, produce living young (larvae) of a similar char- 

 acter, these in turn produce another similar brood, and so on for six 

 or seven generations ; but the last fall brood is composed of both males 

 and females ; these females deposit eggs for the next spring brood. 



The descriptions of species given in this report, as is usually the 

 case with entomological works, apply almost exclusively to the per- 

 fect insects, but the readers for whom our State reports are especiallv 

 mtended, as a rule first discover injurious species when in the larva 

 state, and are desirous of ascertaining at once what they are, at least 

 with sufficient accuracy to have a general knowledge of their habits 

 and of the remedies recommended. Taking up an entomological re- 

 port or work they know not where .to begin or how to ascertain 

 whether their insect is described or not. In order to aid in this mat- 

 ter, I will give some general directions, it being, as I have already in- 

 timated, impossible to give more than general directions by charac- 

 ters of the larvae alone, but as a general rule if Ave can trace them to 

 the family to which they belong we can form a tolerably correct idea 

 of their habits, and if we can do this, a little search through the de- 

 scriptions ot the species of the family may enable us to find it if men- 

 tioned in the work we are examining. 



The reader should understand that the directions given here apply 

 only to the larvae of insects found injurious to vegetation in Illinois 

 and which are mentioned in this report, or are closely allied to some 

 species herein described. 



First— Larvae, which are similar to the perfect insect, and which do 

 not ceaso to eat when they arrive at the pupa state. These, as we 

 have seen, belong to the orders of Orthoptera and Hemiptera, as these 

 are the only orders which have active pupae (the exceptions found in 

 Neuroptera need not be considered here). If belonging to the former 

 order, and injurious or troublesome to an extent worthy of attention 

 they must be cockroaches, crickets, or grasshoppers, and may be recog- 

 nized by their biting jaws and resemblance to these insects in the 

 perfect state. If they are Hemiptcrous they may be known by the 

 horny jointed bill which is turned under the breast when at rest, and 

 with which they pierce the bark, leaves and tender portions of the 

 plants; this fact will show at once which order they belong to and 

 their genera] resemblance to the perfect insect they make will assist 

 m determining the family. 



In the second place, we may take it for granted thatalarva which is a 

 grub, caterpillar, maggot, or slug, or thai can be considered worm-like, 

 whether with a head or without, with feet or without them, long or 

 short, thick or thin, smooth, covered with hairs or spined, flat or 

 round, cannot belong either to the Orthoptera or Hemiptera. If it is in- 



