I 



LEAF-FEEDING INSECTS OF SHADE TREES 



By W. B. Becker, Research Assistant in Entomology' 



Introduction 



The purpose of this bulletin is to make available to the people of Massachusetts 1 

 information regarding the habits and control of the more important insect pests 

 defoliating the broad-leaved, deciduous shade and forest trees in the Common- 

 wealth. The insects discussed are the ones commonly encountered and, in addi 

 tion, a few species which have not been reported from Massachusetts but are close 

 to its borders. An account of injury caused by red spiders, or mites, is also 

 included, as well as of the various types of damage caused by squirrels but some 

 times mistaken for insect work. 



The life histories are subject to some variation from year to year depending on 

 the seasonal climatic conditions. 



As far as possible, technical terms and expressions have been avoided. How 

 ever, because the common name given to the insects often varies with the locality, 

 the scientific name is also given for reference purposes. Some of the terms dealing 

 with the various life stages, transformations, and structures of the insects are 

 included. Briefly, these are as follows: 



Life History of Insects. Moths, butterflies, sawflies, and beetles pass through 

 four distinct life stages: egg, larva, pupa, and adult. The egg hatches into a 

 wormlike creature known as a larva. Larvae of moths and butterflies are com- 

 monly referred to as caterpillars; the legless larvae of certain moths as slug cater- 

 pillars; sawfly larvae as false caterpillars; and beetle larvae as grubs. A larva 

 grows by shedding its skin several times, each time producing a new skin larger 

 than the previous one — a process commonly called molting. After molting a 

 few times, a larva becomes full grown, or mature, and transforms into a pupa. 

 This is a resting stage during which the larval form is destroyed and the adult 

 form developed. The transformation may occur inside a covering — a cocoon 

 for sawflies and moths, a chr>-salid for butterflies, a pupal cell for beetles; or it 

 may occur in the absence of a covering, when the pupa is often referred to as being 

 naked. When the transformation is complete, the moth, butterfly, sawfly, or 

 beetle appears. The adult is entirely different in form from the larva so that these 

 insects are said to have a complete metamorphosis. After mating, the female 

 deposits her eggs and the life cycle is repeated. 



The development of walkingsticks and spider-mites diff^ers from the above 

 in that the young, called n>mphs, have the general form and appearance of the 

 adults. They also go through the process of molting. After each succeeding molt 

 the nymph more closely resembles the adult until it transforms to the adult stage 

 directly without first passing through a pupal, or resting, stage. These are said 

 to have an incomplete metamorphosis. 



Structure of an Insect. The bod>' of an insect is divided into three parts: head, 

 thorax, and abdomen. To the head are attached the antennae, or feelers, the 

 eyes, and mouth parts. Directly behind the head is the thorax, to which are at- 

 tached the wings and true legs. The posterior section is the abdomen. Moths, 



^The writer acknowledges with sincere appreciation the valuable assistance in the preparation 

 of the bulletin which was rendered by A. I. Bourne. Research Professor of Entomology, and by 

 W. E. Tomlinson, temporary assistant in the department, as well as the assistance of colleges, ex- 

 periment stations, publishing companies and individuals in connection with the illustrative material. 



